diff --git a/composer.json b/composer.json
index 0b0a2a7c..ffeae7d2 100644
--- a/composer.json
+++ b/composer.json
@@ -20,14 +20,15 @@
         "wp-cli/extension-command": "^1.2 || ^2",
         "wp-cli/media-command": "^1.1 || ^2",
         "wp-cli/super-admin-command": "^1 || ^2",
-        "wp-cli/wp-cli-tests": "^4"
+        "wp-cli/wp-cli-tests": "dev-main"
     },
     "config": {
         "process-timeout": 7200,
         "sort-packages": true,
         "allow-plugins": {
             "dealerdirect/phpcodesniffer-composer-installer": true,
-            "johnpbloch/wordpress-core-installer": true
+            "johnpbloch/wordpress-core-installer": true,
+            "phpstan/extension-installer": true
         },
         "lock": false
     },
@@ -230,12 +231,14 @@
         "behat-rerun": "rerun-behat-tests",
         "lint": "run-linter-tests",
         "phpcs": "run-phpcs-tests",
+        "phpstan": "run-phpstan-tests",
         "phpunit": "run-php-unit-tests",
         "phpcbf": "run-phpcbf-cleanup",
         "prepare-tests": "install-package-tests",
         "test": [
             "@lint",
             "@phpcs",
+            "@phpstan",
             "@phpunit",
             "@behat"
         ]
diff --git a/entity-command.php b/entity-command.php
index 2146f886..6cb54ff3 100644
--- a/entity-command.php
+++ b/entity-command.php
@@ -60,17 +60,7 @@
 );
 WP_CLI::add_command( 'taxonomy', 'Taxonomy_Command' );
 WP_CLI::add_command( 'term', 'Term_Command' );
-WP_CLI::add_command(
-	'term meta',
-	'Term_Meta_Command',
-	array(
-		'before_invoke' => function () {
-			if ( Utils\wp_version_compare( '4.4', '<' ) ) {
-				WP_CLI::error( 'Requires WordPress 4.4 or greater.' );
-			}
-		},
-	)
-);
+WP_CLI::add_command( 'term meta', 'Term_Meta_Command' );
 WP_CLI::add_command( 'user', 'User_Command' );
 WP_CLI::add_command(
 	'user application-password',
@@ -84,17 +74,7 @@
 	)
 );
 WP_CLI::add_command( 'user meta', 'User_Meta_Command' );
-WP_CLI::add_command(
-	'user session',
-	'User_Session_Command',
-	array(
-		'before_invoke' => function () {
-			if ( Utils\wp_version_compare( '4.0', '<' ) ) {
-				WP_CLI::error( 'Requires WordPress 4.0 or greater.' );
-			}
-		},
-	)
-);
+WP_CLI::add_command( 'user session', 'User_Session_Command' );
 WP_CLI::add_command( 'user term', 'User_Term_Command' );
 
 if ( class_exists( 'WP_CLI\Dispatcher\CommandNamespace' ) ) {
diff --git a/features/post.feature b/features/post.feature
index c3f72a52..858668bf 100644
--- a/features/post.feature
+++ b/features/post.feature
@@ -451,40 +451,6 @@ Feature: Manage WordPress posts
       Test Post
       """
 
-  @less-than-wp-4.4
-  Scenario: Creating/updating posts with meta keys for WP < 4.4 has no effect so should give warning
-    When I try `wp post create --post_title='Test Post' --post_content='Test post content' --meta_input='{"key1":"value1","key2":"value2"}' --porcelain`
-    Then the return code should be 0
-    And STDOUT should be a number
-    And save STDOUT as {POST_ID}
-    And STDERR should be:
-      """
-      Warning: The 'meta_input' field was only introduced in WordPress 4.4 so will have no effect.
-      """
-
-    When I run `wp post meta list {POST_ID} --format=count`
-    Then STDOUT should be:
-      """
-      0
-      """
-
-    When I try `wp post update {POST_ID} --meta_input='{"key2":"value2b","key3":"value3"}'`
-    Then the return code should be 0
-    And STDERR should be:
-      """
-      Warning: The 'meta_input' field was only introduced in WordPress 4.4 so will have no effect.
-      """
-    And STDOUT should be:
-      """
-      Success: Updated post {POST_ID}.
-      """
-
-    When I run `wp post meta list {POST_ID} --format=count`
-    Then STDOUT should be:
-      """
-      0
-      """
-
   Scenario: Publishing a post and setting a date fails if the edit_date flag is not passed.
     Given a WP install
 
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
new file mode 100644
index 00000000..5cf50e82
--- /dev/null
+++ b/phpstan.neon.dist
@@ -0,0 +1,20 @@
+parameters:
+  level: 6
+  paths:
+    - src
+    - entity-command.php
+  scanDirectories:
+    - vendor/wp-cli/wp-cli/php
+    - vendor/wp-cli/wp-cli-tests
+  scanFiles:
+    - vendor/php-stubs/wordpress-stubs/wordpress-stubs.php
+  treatPhpDocTypesAsCertain: false
+  dynamicConstantNames:
+  	- WP_DEBUG
+  	- WP_DEBUG_LOG
+  	- WP_DEBUG_DISPLAY
+  ignoreErrors:
+    - identifier: missingType.iterableValue
+    - identifier: missingType.property
+    - identifier: missingType.parameter
+    - identifier: missingType.return
diff --git a/src/Comment_Command.php b/src/Comment_Command.php
index 0661ba91..c11dc1d0 100644
--- a/src/Comment_Command.php
+++ b/src/Comment_Command.php
@@ -243,6 +243,7 @@ public function get( $args, $assoc_args ) {
 		}
 
 		if ( ! isset( $comment->url ) ) {
+			// @phpstan-ignore property.notFound
 			$comment->url = get_comment_link( $comment );
 		}
 
@@ -366,6 +367,8 @@ public function get( $args, $assoc_args ) {
 	public function list_( $args, $assoc_args ) {
 		$formatter = $this->get_formatter( $assoc_args );
 
+		// To be fixed in wp-cli/wp-cli.
+		// @phpstan-ignore property.notFound
 		if ( 'ids' === $formatter->format ) {
 			$assoc_args['fields'] = 'comment_ID';
 		}
@@ -376,29 +379,22 @@ public function list_( $args, $assoc_args ) {
 			$assoc_args['count'] = true;
 		}
 
-		if ( ! empty( $assoc_args['comment__in'] )
-			&& ! empty( $assoc_args['orderby'] )
-			&& 'comment__in' === $assoc_args['orderby']
-			&& Utils\wp_version_compare( '4.4', '<' ) ) {
-			$comments = [];
-			foreach ( $assoc_args['comment__in'] as $comment_id ) {
-				$comment = get_comment( $comment_id );
-				if ( $comment ) {
-					$comments[] = $comment;
-				} else {
-					WP_CLI::warning( "Invalid comment {$comment_id}." );
-				}
-			}
-		} else {
-			$query    = new WP_Comment_Query();
-			$comments = $query->query( $assoc_args );
-		}
+		$query    = new WP_Comment_Query();
+		$comments = $query->query( $assoc_args );
 
 		if ( 'count' === $formatter->format ) {
+			/**
+			 * @var int $comments
+			 */
 			echo $comments;
 		} else {
 			if ( 'ids' === $formatter->format ) {
-				$comments = wp_list_pluck( $comments, 'comment_ID' );
+				/**
+				 * @var \WP_Comment[] $comments
+				 */
+				$items = wp_list_pluck( $comments, 'comment_ID' );
+
+				$comments = $items;
 			} elseif ( is_array( $comments ) ) {
 				$comments = array_map(
 					function ( $comment ) {
@@ -439,7 +435,7 @@ public function delete( $args, $assoc_args ) {
 			$args,
 			$assoc_args,
 			function ( $comment_id, $assoc_args ) {
-				$force = Utils\get_flag_value( $assoc_args, 'force' );
+				$force = (bool) Utils\get_flag_value( $assoc_args, 'force' );
 
 				$status = wp_get_comment_status( $comment_id );
 				$result = wp_delete_comment( $comment_id, $force );
@@ -457,6 +453,9 @@ function ( $comment_id, $assoc_args ) {
 	private function call( $args, $status, $success, $failure ) {
 		$comment_id = absint( $args );
 
+		/**
+		 * @var callable $func
+		 */
 		$func = "wp_{$status}_comment";
 
 		if ( ! $func( $comment_id ) ) {
@@ -642,16 +641,17 @@ public function unapprove( $args, $assoc_args ) {
 	 *     total_comments:  19
 	 */
 	public function count( $args, $assoc_args ) {
-		$post_id = Utils\get_flag_value( $args, 0, 0 );
+		$post_id = $args[0] ?? null;
 
 		$count = wp_count_comments( $post_id );
 
 		// Move total_comments to the end of the object
 		$total = $count->total_comments;
 		unset( $count->total_comments );
+		// @phpstan-ignore assign.propertyReadOnly
 		$count->total_comments = $total;
 
-		foreach ( $count as $status => $count ) {
+		foreach ( (array) $count as $status => $count ) {
 			WP_CLI::line( str_pad( "$status:", 17 ) . $count );
 		}
 	}
@@ -673,6 +673,9 @@ public function count( $args, $assoc_args ) {
 	public function recount( $args ) {
 		foreach ( $args as $id ) {
 			if ( wp_update_comment_count( $id ) ) {
+				/**
+				 * @var \WP_Post $post
+				 */
 				$post = get_post( $id );
 				WP_CLI::log( "Updated post {$post->ID} comment count to {$post->comment_count}." );
 			} else {
diff --git a/src/Comment_Meta_Command.php b/src/Comment_Meta_Command.php
index 7cb01821..38b6c398 100644
--- a/src/Comment_Meta_Command.php
+++ b/src/Comment_Meta_Command.php
@@ -104,11 +104,11 @@ protected function delete_metadata( $object_id, $meta_key, $meta_value = '' ) {
 	/**
 	 * Check that the comment ID exists
 	 *
-	 * @param int
+	 * @param int $object_id
 	 */
 	protected function check_object_id( $object_id ) {
 		$fetcher = new CommentFetcher();
-		$comment = $fetcher->get_check( $object_id );
+		$comment = $fetcher->get_check( (string) $object_id );
 		return $comment->comment_ID;
 	}
 }
diff --git a/src/Menu_Command.php b/src/Menu_Command.php
index e6806530..b23df5c7 100644
--- a/src/Menu_Command.php
+++ b/src/Menu_Command.php
@@ -70,7 +70,7 @@ public function create( $args, $assoc_args ) {
 
 		} elseif ( Utils\get_flag_value( $assoc_args, 'porcelain' ) ) {
 
-				WP_CLI::line( $menu_id );
+				WP_CLI::line( (string) $menu_id );
 		} else {
 			WP_CLI::success( "Created menu {$menu_id}." );
 		}
@@ -166,6 +166,7 @@ public function list_( $args, $assoc_args ) {
 		$menu_locations = get_nav_menu_locations();
 		foreach ( $menus as &$menu ) {
 
+			// @phpstan-ignore property.notFound
 			$menu->locations = [];
 			foreach ( $menu_locations as $location => $term_id ) {
 
diff --git a/src/Menu_Item_Command.php b/src/Menu_Item_Command.php
index c61d9f7d..418d3fa4 100644
--- a/src/Menu_Item_Command.php
+++ b/src/Menu_Item_Command.php
@@ -92,7 +92,7 @@ class Menu_Item_Command extends WP_CLI_Command {
 	public function list_( $args, $assoc_args ) {
 
 		$items = wp_get_nav_menu_items( $args[0] );
-		if ( false === $items || is_wp_error( $items ) ) {
+		if ( false === $items ) {
 			WP_CLI::error( 'Invalid menu.' );
 		}
 
@@ -408,10 +408,10 @@ public function delete( $args, $assoc_args ) {
 	private function add_or_update_item( $method, $type, $args, $assoc_args ) {
 
 		$menu            = $args[0];
-		$menu_item_db_id = Utils\get_flag_value( $args, 1, 0 );
+		$menu_item_db_id = $args[1] ?? 0;
 
 		$menu = wp_get_nav_menu_object( $menu );
-		if ( ! $menu || is_wp_error( $menu ) ) {
+		if ( false === $menu ) {
 			WP_CLI::error( 'Invalid menu.' );
 		}
 
@@ -422,6 +422,14 @@ private function add_or_update_item( $method, $type, $args, $assoc_args ) {
 		if ( 'update' === $method ) {
 
 			$menu_item_obj = get_post( $menu_item_db_id );
+
+			if ( ! $menu_item_obj ) {
+				WP_CLI::error( 'Invalid menu.' );
+			}
+
+			/**
+			 * @var object{title: string, url: string, description: string, object: string, object_id: int, menu_item_parent: int, attr_title: string, target: string, classes: string[], xfn: string, post_status: string, menu_order: int} $menu_item_obj
+			 */
 			$menu_item_obj = wp_setup_nav_menu_item( $menu_item_obj );
 
 			// Correct the menu position if this was the first item. See https://core.trac.wordpress.org/ticket/28140
@@ -502,7 +510,7 @@ private function add_or_update_item( $method, $type, $args, $assoc_args ) {
 			}
 
 			if ( 'add' === $method && ! empty( $assoc_args['porcelain'] ) ) {
-				WP_CLI::line( $result );
+				WP_CLI::line( (string) $result );
 			} elseif ( 'add' === $method ) {
 					WP_CLI::success( 'Menu item added.' );
 			} elseif ( 'update' === $method ) {
diff --git a/src/Menu_Location_Command.php b/src/Menu_Location_Command.php
index 540c87e4..a5bc555d 100644
--- a/src/Menu_Location_Command.php
+++ b/src/Menu_Location_Command.php
@@ -77,6 +77,8 @@ public function list_( $args, $assoc_args ) {
 
 		$formatter = new Formatter( $assoc_args, [ 'location', 'description' ] );
 
+		// To be fixed in wp-cli/wp-cli.
+		// @phpstan-ignore property.notFound
 		if ( 'ids' === $formatter->format ) {
 			$ids = array_map(
 				function ( $o ) {
@@ -107,6 +109,8 @@ function ( $o ) {
 	 *     Success: Assigned location primary to menu primary-menu.
 	 *
 	 * @subcommand assign
+	 *
+	 * @param array{string, string} $args
 	 */
 	public function assign( $args, $assoc_args ) {
 
@@ -147,18 +151,20 @@ public function assign( $args, $assoc_args ) {
 	 *     Success: Removed location from menu.
 	 *
 	 * @subcommand remove
+	 *
+	 * @param array{string, string} $args
 	 */
 	public function remove( $args, $assoc_args ) {
 
 		list( $menu, $location ) = $args;
 
 		$menu = wp_get_nav_menu_object( $menu );
-		if ( ! $menu || is_wp_error( $menu ) ) {
+		if ( false === $menu ) {
 			WP_CLI::error( 'Invalid menu.' );
 		}
 
 		$locations = get_nav_menu_locations();
-		if ( Utils\get_flag_value( $locations, $location ) !== $menu->term_id ) {
+		if ( ( $locations[ $location ] ?? null ) !== $menu->term_id ) {
 			WP_CLI::error( "Menu isn't assigned to location." );
 		}
 
diff --git a/src/Option_Command.php b/src/Option_Command.php
index 73bc32b2..d9f3a60e 100644
--- a/src/Option_Command.php
+++ b/src/Option_Command.php
@@ -133,6 +133,7 @@ public function add( $args, $assoc_args ) {
 			$autoload = 'yes';
 		}
 
+		// @phpstan-ignore argument.type
 		if ( ! add_option( $key, $value, '', $autoload ) ) {
 			WP_CLI::error( "Could not add option '{$key}'. Does it already exist?" );
 		} else {
@@ -321,8 +322,8 @@ public function list_( $args, $assoc_args ) {
 				function ( $a, $b ) use ( $orderby, $order ) {
 					// Sort array.
 					return 'asc' === $order
-						? $a->$orderby > $b->$orderby
-						: $a->$orderby < $b->$orderby;
+						? $a->$orderby <=> $b->$orderby
+						: $b->$orderby <=> $a->$orderby;
 				}
 			);
 		} elseif ( 'option_id' === $orderby && 'desc' === $order ) { // Sort by default descending.
@@ -422,7 +423,11 @@ public function update( $args, $assoc_args ) {
 			$autoload = null;
 		}
 
+		/**
+		 * @var string $value
+		 */
 		$value = sanitize_option( $key, $value );
+
 		// Sanitization WordPress normally performs when getting an option
 		if ( in_array( $key, [ 'siteurl', 'home', 'category_base', 'tag_base' ], true ) ) {
 			$value = untrailingslashit( $value );
@@ -431,6 +436,7 @@ public function update( $args, $assoc_args ) {
 
 		if ( $value === $old_value && null === $autoload ) {
 			WP_CLI::success( "Value passed for '{$key}' option is unchanged." );
+			// @phpstan-ignore argument.type
 		} elseif ( update_option( $key, $value, $autoload ) ) {
 				WP_CLI::success( "Updated '{$key}' option." );
 		} else {
@@ -744,17 +750,11 @@ function ( $key ) {
 	}
 
 	private static function esc_like( $old ) {
+		/**
+		 * @var \wpdb $wpdb
+		 */
 		global $wpdb;
 
-		// Remove notices in 4.0 and support backwards compatibility
-		if ( method_exists( $wpdb, 'esc_like' ) ) {
-			// 4.0
-			$old = $wpdb->esc_like( $old );
-		} else {
-			// phpcs:ignore WordPress.WP.DeprecatedFunctions.like_escapeFound -- called in WordPress 3.9 or less.
-			$old = like_escape( esc_sql( $old ) );
-		}
-
-		return $old;
+		return $wpdb->esc_like( $old );
 	}
 }
diff --git a/src/Post_Command.php b/src/Post_Command.php
index a4a5ba42..a9c1a60e 100644
--- a/src/Post_Command.php
+++ b/src/Post_Command.php
@@ -182,10 +182,6 @@ public function create( $args, $assoc_args ) {
 			$assoc_args['post_category'] = $this->get_category_ids( $assoc_args['post_category'] );
 		}
 
-		if ( isset( $assoc_args['meta_input'] ) && Utils\wp_version_compare( '4.4', '<' ) ) {
-			WP_CLI::warning( "The 'meta_input' field was only introduced in WordPress 4.4 so will have no effect." );
-		}
-
 		$array_arguments = [ 'meta_input' ];
 		$assoc_args      = Utils\parse_shell_arrays( $assoc_args, $array_arguments );
 
@@ -351,10 +347,6 @@ public function update( $args, $assoc_args ) {
 			$assoc_args['post_category'] = $this->get_category_ids( $assoc_args['post_category'] );
 		}
 
-		if ( isset( $assoc_args['meta_input'] ) && Utils\wp_version_compare( '4.4', '<' ) ) {
-			WP_CLI::warning( "The 'meta_input' field was only introduced in WordPress 4.4 so will have no effect." );
-		}
-
 		$array_arguments = [ 'meta_input' ];
 		$assoc_args      = Utils\parse_shell_arrays( $assoc_args, $array_arguments );
 
@@ -387,7 +379,7 @@ public function edit( $args, $assoc_args ) {
 		$result = $this->_edit( $post->post_content, "WP-CLI post {$post->ID}" );
 
 		if ( false === $result ) {
-			WP_CLI::warning( 'No change made to post content.', 'Aborted' );
+			WP_CLI::warning( 'No change made to post content.' );
 		} else {
 			$this->update( $args, [ 'post_content' => $result ] );
 		}
@@ -644,9 +636,12 @@ public function list_( $args, $assoc_args ) {
 			$query_args['post_type'] = explode( ',', $query_args['post_type'] );
 		}
 
+		// To be fixed in wp-cli/wp-cli.
+		// @phpstan-ignore property.notFound
 		if ( 'ids' === $formatter->format ) {
 			$query_args['fields'] = 'ids';
 			$query                = new WP_Query( $query_args );
+			// @phpstan-ignore argument.type
 			echo implode( ' ', $query->posts );
 		} elseif ( 'count' === $formatter->format ) {
 			$query_args['fields'] = 'ids';
@@ -656,8 +651,13 @@ public function list_( $args, $assoc_args ) {
 			$query = new WP_Query( $query_args );
 			$posts = array_map(
 				function ( $post ) {
-						$post->url = get_permalink( $post->ID );
-						return $post;
+					/**
+					 * @var \WP_Post $post
+					 */
+
+					// @phpstan-ignore property.notFound
+					$post->url = get_permalink( $post->ID );
+					return $post;
 				},
 				$query->posts
 			);
@@ -806,11 +806,14 @@ public function generate( $args, $assoc_args ) {
 		// Get the total number of posts.
 		$total = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->posts WHERE post_type = %s", $post_data['post_type'] ) );
 
+		/**
+		 * @var \WP_Post_Type $post_type
+		 */
+		$post_type = get_post_type_object( $post_data['post_type'] );
+
 		$label = ! empty( $post_data['post_title'] )
 			? $post_data['post_title']
-			: get_post_type_object( $post_data['post_type'] )->labels->singular_name;
-
-		$hierarchical = get_post_type_object( $post_data['post_type'] )->hierarchical;
+			: $post_type->labels->singular_name;
 
 		$limit = $post_data['count'] + $total;
 
@@ -827,7 +830,7 @@ public function generate( $args, $assoc_args ) {
 
 		for ( $index = $total; $index < $limit; $index++ ) {
 
-			if ( $hierarchical ) {
+			if ( $post_type->hierarchical ) {
 
 				if ( $this->maybe_make_child() && $current_depth < $post_data['max_depth'] ) {
 
@@ -933,7 +936,7 @@ private function read_from_file_or_stdin( $arg ) {
 		} else {
 			$readfile = 'php://stdin';
 		}
-		return file_get_contents( $readfile );
+		return (string) file_get_contents( $readfile );
 	}
 
 	/**
@@ -1010,7 +1013,7 @@ private function get_category( $post_id ) {
 	private function get_tags( $post_id ) {
 		$tag_data = get_the_tags( $post_id );
 		$tag_arr  = [];
-		if ( $tag_data ) {
+		if ( $tag_data && ! is_wp_error( $tag_data ) ) {
 			foreach ( $tag_data as $tag ) {
 				array_push( $tag_arr, $tag->slug );
 			}
diff --git a/src/Post_Meta_Command.php b/src/Post_Meta_Command.php
index 96aa2341..f225851d 100644
--- a/src/Post_Meta_Command.php
+++ b/src/Post_Meta_Command.php
@@ -30,11 +30,11 @@ class Post_Meta_Command extends CommandWithMeta {
 	/**
 	 * Check that the post ID exists
 	 *
-	 * @param int
+	 * @param int $object_id
 	 */
 	protected function check_object_id( $object_id ) {
 		$fetcher = new PostFetcher();
-		$post    = $fetcher->get_check( $object_id );
+		$post    = $fetcher->get_check( (string) $object_id );
 		return $post->ID;
 	}
 
diff --git a/src/Post_Type_Command.php b/src/Post_Type_Command.php
index 88c01029..335477bc 100644
--- a/src/Post_Type_Command.php
+++ b/src/Post_Type_Command.php
@@ -147,8 +147,9 @@ public function list_( $args, $assoc_args ) {
 
 		$types = array_map(
 			function ( $type ) use ( $counts ) {
-					$type->count = isset( $counts[ $type->name ] ) ? $counts[ $type->name ] : 0;
-					return $type;
+				// @phpstan-ignore property.notFound
+				$type->count = isset( $counts[ $type->name ] ) ? $counts[ $type->name ] : 0;
+				return $type;
 			},
 			$types
 		);
diff --git a/src/Signup_Command.php b/src/Signup_Command.php
index 4144257e..4125ceea 100644
--- a/src/Signup_Command.php
+++ b/src/Signup_Command.php
@@ -130,9 +130,12 @@ public function list_( $args, $assoc_args ) {
 
 		$signups = array();
 
-		$per_page = (int) Utils\get_flag_value( $assoc_args, 'per_page' );
+		/**
+		 * @var string|null $per_page
+		 */
+		$per_page = Utils\get_flag_value( $assoc_args, 'per_page' );
 
-		$limit = $per_page ? $wpdb->prepare( 'LIMIT %d', $per_page ) : '';
+		$limit = $per_page ? $wpdb->prepare( 'LIMIT %d', (int) $per_page ) : '';
 
 		$query = "SELECT * FROM $wpdb->signups {$limit}";
 
@@ -308,7 +311,7 @@ public function delete( $args, $assoc_args ) {
 	/**
 	 * Deletes signup.
 	 *
-	 * @param stdClasss $signup
+	 * @param object{signup_id: int|string} $signup
 	 * @return bool True if success; otherwise false.
 	 */
 	private function delete_signup( $signup ) {
diff --git a/src/Site_Command.php b/src/Site_Command.php
index de5451a5..132e080c 100644
--- a/src/Site_Command.php
+++ b/src/Site_Command.php
@@ -29,6 +29,8 @@
  *     Success: The site at 'http://www.example.com/example' was deleted.
  *
  * @package wp-cli
+ *
+ * @phpstan-type UserSite object{userblog_id: int, blogname: string, domain: string, path: string, site_id: int, siteurl: string, archived: int, spam: int, deleted: int}
  */
 class Site_Command extends CommandWithDBObject {
 
@@ -89,6 +91,9 @@ private function empty_posts() {
 	 * Delete terms, taxonomies, and tax relationships.
 	 */
 	private function empty_taxonomies() {
+		/**
+		 * @var \wpdb $wpdb
+		 */
 		global $wpdb;
 
 		// Empty taxonomies and terms
@@ -278,6 +283,10 @@ public function empty_( $args, $assoc_args ) {
 			$files_to_unlink       = [];
 			$directories_to_delete = [];
 			$is_main_site          = is_main_site();
+
+			/**
+			 * @var \SplFileInfo $fileinfo
+			 */
 			foreach ( $files as $fileinfo ) {
 				$realpath = $fileinfo->getRealPath();
 				// Don't clobber subsites when operating on the main site
@@ -360,7 +369,7 @@ public function delete( $args, $assoc_args ) {
 
 		WP_CLI::confirm( "Are you sure you want to delete the '{$site_url}' site?", $assoc_args );
 
-		wpmu_delete_blog( $blog->blog_id, ! Utils\get_flag_value( $assoc_args, 'keep-tables' ) );
+		wpmu_delete_blog( (int) $blog->blog_id, ! Utils\get_flag_value( $assoc_args, 'keep-tables' ) );
 
 		WP_CLI::success( "The site at '{$site_url}' was deleted." );
 	}
@@ -400,7 +409,11 @@ public function create( $args, $assoc_args ) {
 
 		global $wpdb, $current_site;
 
-		$base  = $assoc_args['slug'];
+		$base = $assoc_args['slug'];
+
+		/**
+		 * @var string $title
+		 */
 		$title = Utils\get_flag_value( $assoc_args, 'title', ucfirst( $base ) );
 
 		$email = empty( $assoc_args['email'] ) ? '' : $assoc_args['email'];
@@ -479,7 +492,7 @@ public function create( $args, $assoc_args ) {
 		}
 
 		if ( Utils\get_flag_value( $assoc_args, 'porcelain' ) ) {
-			WP_CLI::line( $id );
+			WP_CLI::line( (string) $id );
 		} else {
 			$site_url = trailingslashit( get_site_url( $id ) );
 			WP_CLI::success( "Site {$id} created: {$site_url}" );
@@ -806,6 +819,9 @@ public function list_( $args, $assoc_args ) {
 			$user = ( new UserFetcher() )->get_check( $assoc_args['site_user'] );
 
 			if ( $user ) {
+				/**
+				 * @phpstan-var UserSite[] $blogs
+				 */
 				$blogs = get_blogs_of_user( $user->ID );
 
 				foreach ( $blogs as $blog ) {
@@ -830,6 +846,9 @@ public function list_( $args, $assoc_args ) {
 
 		$iterator = new TableIterator( $iterator_args );
 
+		/**
+		 * @var iterable $iterator
+		 */
 		$iterator = Utils\iterator_map(
 			$iterator,
 			function ( $blog ) {
@@ -1142,6 +1161,8 @@ public function set_private( $args, $assoc_args ) {
 	private function update_site_status( $ids, $pref, $value ) {
 		$value = (int) $value;
 
+		$action = 'updated';
+
 		switch ( $pref ) {
 			case 'archived':
 				$action = $value ? 'archived' : 'unarchived';
@@ -1175,7 +1196,7 @@ private function update_site_status( $ids, $pref, $value ) {
 				continue;
 			}
 
-			update_blog_status( $site->blog_id, $pref, $value );
+			update_blog_status( $site->blog_id, $pref, (string) $value );
 			WP_CLI::success( "Site {$site->blog_id} {$action}." );
 		}
 	}
@@ -1190,6 +1211,9 @@ private function update_site_status( $ids, $pref, $value ) {
 	 * @throws ExitException
 	 */
 	private function get_sites_ids( $args, $assoc_args ) {
+		/**
+		 * @var string|false $slug
+		 */
 		$slug = Utils\get_flag_value( $assoc_args, 'slug', false );
 
 		if ( $slug ) {
diff --git a/src/Site_Meta_Command.php b/src/Site_Meta_Command.php
index acc58741..e9bcfadb 100644
--- a/src/Site_Meta_Command.php
+++ b/src/Site_Meta_Command.php
@@ -30,11 +30,11 @@ class Site_Meta_Command extends CommandWithMeta {
 	/**
 	 * Check that the site ID exists
 	 *
-	 * @param int
+	 * @param int $object_id
 	 */
 	protected function check_object_id( $object_id ) {
 		$fetcher = new SiteFetcher();
-		$site    = $fetcher->get_check( $object_id );
+		$site    = $fetcher->get_check( (string) $object_id );
 		return $site->blog_id;
 	}
 
diff --git a/src/Site_Option_Command.php b/src/Site_Option_Command.php
index b2a96883..c4e9e4b4 100644
--- a/src/Site_Option_Command.php
+++ b/src/Site_Option_Command.php
@@ -406,17 +406,11 @@ function ( $key ) {
 	}
 
 	private static function esc_like( $old ) {
+		/**
+		 * @var \wpdb $wpdb
+		 */
 		global $wpdb;
 
-		// Remove notices in 4.0 and support backwards compatibility
-		if ( method_exists( $wpdb, 'esc_like' ) ) {
-			// 4.0
-			$old = $wpdb->esc_like( $old );
-		} else {
-			// phpcs:ignore WordPress.WP.DeprecatedFunctions.like_escapeFound -- called in WordPress 3.9 or less.
-			$old = like_escape( esc_sql( $old ) );
-		}
-
-		return $old;
+		return $wpdb->esc_like( $old );
 	}
 }
diff --git a/src/Taxonomy_Command.php b/src/Taxonomy_Command.php
index 1f1d05f9..8bae2961 100644
--- a/src/Taxonomy_Command.php
+++ b/src/Taxonomy_Command.php
@@ -38,16 +38,6 @@ class Taxonomy_Command extends WP_CLI_Command {
 		'public',
 	);
 
-	public function __construct() {
-
-		if ( Utils\wp_version_compare( 3.7, '<' ) ) {
-			// remove description for wp <= 3.7
-			$this->fields = array_values( array_diff( $this->fields, array( 'description' ) ) );
-		}
-
-		parent::__construct();
-	}
-
 	/**
 	 * Gets the term counts for each supplied taxonomy.
 	 *
@@ -173,8 +163,11 @@ public function list_( $args, $assoc_args ) {
 
 		$taxonomies = array_map(
 			function ( $taxonomy ) use ( $counts ) {
+					// @phpstan-ignore assign.propertyType
 					$taxonomy->object_type = implode( ', ', $taxonomy->object_type );
-					$taxonomy->count       = isset( $counts[ $taxonomy->name ] ) ? $counts[ $taxonomy->name ] : 0;
+
+					// @phpstan-ignore property.notFound
+					$taxonomy->count = isset( $counts[ $taxonomy->name ] ) ? $counts[ $taxonomy->name ] : 0;
 					return $taxonomy;
 			},
 			$taxonomies
diff --git a/src/Term_Command.php b/src/Term_Command.php
index e0218909..489ddf3e 100644
--- a/src/Term_Command.php
+++ b/src/Term_Command.php
@@ -133,23 +133,15 @@ public function list_( $args, $assoc_args ) {
 		$assoc_args = array_merge( $defaults, $assoc_args );
 
 		if ( ! empty( $assoc_args['term_id'] ) ) {
+			/**
+			 * @var \WP_Term $term
+			 */
 			$term  = get_term_by( 'id', $assoc_args['term_id'], $args[0] );
 			$terms = [ $term ];
-		} elseif ( ! empty( $assoc_args['include'] )
-			&& ! empty( $assoc_args['orderby'] )
-			&& 'include' === $assoc_args['orderby']
-			&& Utils\wp_version_compare( '4.7', '<' ) ) {
-			$terms    = [];
-			$term_ids = explode( ',', $assoc_args['include'] );
-			foreach ( $term_ids as $term_id ) {
-				$term = get_term_by( 'id', $term_id, $args[0] );
-				if ( $term && ! is_wp_error( $term ) ) {
-					$terms[] = $term;
-				} else {
-					WP_CLI::warning( "Invalid term {$term_id}." );
-				}
-			}
 		} else {
+			/**
+			 * @var \WP_Term[] $terms
+			 */
 			// phpcs:ignore WordPress.WP.DeprecatedParameters.Get_termsParam2Found -- Required for backward compatibility.
 			$terms = get_terms( $args, $assoc_args );
 		}
@@ -158,7 +150,9 @@ public function list_( $args, $assoc_args ) {
 			function ( $term ) {
 					$term->count  = (int) $term->count;
 					$term->parent = (int) $term->parent;
-					$term->url    = get_term_link( $term );
+
+					// @phpstan-ignore property.notFound
+					$term->url = get_term_link( $term );
 					return $term;
 			},
 			$terms
@@ -215,11 +209,6 @@ public function create( $args, $assoc_args ) {
 		$porcelain = Utils\get_flag_value( $assoc_args, 'porcelain' );
 		unset( $assoc_args['porcelain'] );
 
-		// Compatibility for < WP 4.0
-		if ( $assoc_args['parent'] > 0 && ! term_exists( (int) $assoc_args['parent'] ) ) {
-			WP_CLI::error( 'Parent term does not exist.' );
-		}
-
 		$assoc_args = wp_slash( $assoc_args );
 		$term       = wp_slash( $term );
 		$result     = wp_insert_term( $term, $taxonomy, $assoc_args );
@@ -227,7 +216,7 @@ public function create( $args, $assoc_args ) {
 		if ( is_wp_error( $result ) ) {
 			WP_CLI::error( $result->get_error_message() );
 		} elseif ( $porcelain ) {
-				WP_CLI::line( $result['term_id'] );
+				WP_CLI::line( (string) $result['term_id'] );
 		} else {
 			WP_CLI::success( "Created {$taxonomy} {$result['term_id']}." );
 		}
@@ -284,13 +273,19 @@ public function get( $args, $assoc_args ) {
 
 		list( $taxonomy, $term ) = $args;
 
-		$term = get_term_by( Utils\get_flag_value( $assoc_args, 'by' ), $term, $taxonomy );
+		/**
+		 * @var string $field
+		 */
+		$field = Utils\get_flag_value( $assoc_args, 'by' );
+
+		$term = get_term_by( $field, $term, $taxonomy );
 
 		if ( ! $term ) {
 			WP_CLI::error( "Term doesn't exist." );
 		}
 
 		if ( ! isset( $term->url ) ) {
+			// @phpstan-ignore property.notFound
 			$term->url = get_term_link( $term );
 		}
 
@@ -368,7 +363,12 @@ public function update( $args, $assoc_args ) {
 
 		$assoc_args = wp_slash( $assoc_args );
 
-		$term = get_term_by( Utils\get_flag_value( $assoc_args, 'by' ), $term, $taxonomy );
+		/**
+		 * @var string $field
+		 */
+		$field = Utils\get_flag_value( $assoc_args, 'by' );
+
+		$term = get_term_by( $field, $term, $taxonomy );
 
 		if ( ! $term ) {
 			WP_CLI::error( "Term doesn't exist." );
@@ -528,10 +528,13 @@ public function generate( $args, $assoc_args ) {
 			WP_CLI::error( "'{$taxonomy}' is not a registered taxonomy." );
 		}
 
-		$label = get_taxonomy( $taxonomy )->labels->singular_name;
-		$slug  = sanitize_title_with_dashes( $label );
+		/**
+		 * @var \WP_Taxonomy $tax
+		 */
+		$tax = get_taxonomy( $taxonomy );
 
-		$hierarchical = get_taxonomy( $taxonomy )->hierarchical;
+		$label = $tax->labels->singular_name;
+		$slug  = sanitize_title_with_dashes( $label );
 
 		$format = Utils\get_flag_value( $assoc_args, 'format', 'progress' );
 
@@ -551,7 +554,7 @@ public function generate( $args, $assoc_args ) {
 
 		for ( $index = $max_id + 1; $index <= $max_id + $count; $index++ ) {
 
-			if ( $hierarchical ) {
+			if ( $tax->hierarchical ) {
 
 				if ( $previous_term_id && $this->maybe_make_child() && $current_depth < $max_depth ) {
 
@@ -636,6 +639,10 @@ public function recount( $args ) {
 				WP_CLI::warning( "Taxonomy {$taxonomy} does not exist." );
 			} else {
 
+				/**
+				 * @var \WP_Term[] $terms
+				 */
+
 				// phpcs:ignore WordPress.WP.DeprecatedParameters.Get_termsParam2Found -- Required for backward compatibility.
 				$terms             = get_terms( $taxonomy, [ 'hide_empty' => false ] );
 				$term_taxonomy_ids = wp_list_pluck( $terms, 'term_taxonomy_id' );
@@ -680,17 +687,33 @@ public function recount( $args ) {
 	 *     Success: Migrated the term 'video' from taxonomy 'category' to taxonomy 'post_tag' for 1 post.
 	 */
 	public function migrate( $args, $assoc_args ) {
-		$term_reference       = $args[0];
-		$original_taxonomy    = Utils\get_flag_value( $assoc_args, 'from' );
+		$term_reference = $args[0];
+
+		/**
+		 * @var string $original_taxonomy
+		 */
+		$original_taxonomy = Utils\get_flag_value( $assoc_args, 'from' );
+		/**
+		 * @var string $destination_taxonomy
+		 */
 		$destination_taxonomy = Utils\get_flag_value( $assoc_args, 'to' );
 
-		$term = get_term_by( Utils\get_flag_value( $assoc_args, 'by' ), $term_reference, $original_taxonomy );
+		/**
+		 * @var string $field
+		 */
+		$field = Utils\get_flag_value( $assoc_args, 'by' );
+
+		$term = get_term_by( $field, $term_reference, $original_taxonomy );
 
 		if ( ! $term ) {
 			WP_CLI::error( "Taxonomy term '{$term_reference}' for taxonomy '{$original_taxonomy}' doesn't exist." );
 		}
 
-		$original_taxonomy = get_taxonomy( $original_taxonomy );
+		$tax = get_taxonomy( $original_taxonomy );
+
+		if ( ! $tax ) {
+			WP_CLI::error( "Taxonomy '{$original_taxonomy}' doesn't exist." );
+		}
 
 		$id = wp_insert_term(
 			$term->name,
@@ -706,12 +729,15 @@ public function migrate( $args, $assoc_args ) {
 			WP_CLI::error( $id->get_error_message() );
 		}
 
-		$post_ids = get_objects_in_term( $term->term_id, $original_taxonomy->name );
+		/**
+		 * @var string[] $post_ids
+		 */
+		$post_ids = get_objects_in_term( $term->term_id, $tax->name );
 
 		foreach ( $post_ids as $post_id ) {
-			$type = get_post_type( $post_id );
-			if ( in_array( $type, $original_taxonomy->object_type, true ) ) {
-				$term_taxonomy_id = wp_set_object_terms( $post_id, $id['term_id'], $destination_taxonomy, true );
+			$type = get_post_type( (int) $post_id );
+			if ( in_array( $type, $tax->object_type, true ) ) {
+				$term_taxonomy_id = wp_set_object_terms( (int) $post_id, $id['term_id'], $destination_taxonomy, true );
 
 				if ( is_wp_error( $term_taxonomy_id ) ) {
 					WP_CLI::error( "Failed to assign the term '{$term->slug}' to the post {$post_id}. Reason: " . $term_taxonomy_id->get_error_message() );
@@ -720,14 +746,14 @@ public function migrate( $args, $assoc_args ) {
 				WP_CLI::log( "Term '{$term->slug}' assigned to post {$post_id}." );
 			}
 
-			clean_post_cache( $post_id );
+			clean_post_cache( (int) $post_id );
 		}
 
 		clean_term_cache( $term->term_id );
 
 		WP_CLI::log( "Term '{$term->slug}' migrated." );
 
-		$del = wp_delete_term( $term->term_id, $original_taxonomy->name );
+		$del = wp_delete_term( $term->term_id, $tax->name );
 
 		if ( is_wp_error( $del ) ) {
 			WP_CLI::error( "Failed to delete the term '{$term->slug}'. Reason: " . $del->get_error_message() );
@@ -736,7 +762,7 @@ public function migrate( $args, $assoc_args ) {
 		WP_CLI::log( "Old instance of term '{$term->slug}' removed from its original taxonomy." );
 		$post_count  = count( $post_ids );
 		$post_plural = Utils\pluralize( 'post', $post_count );
-		WP_CLI::success( "Migrated the term '{$term->slug}' from taxonomy '{$original_taxonomy->name}' to taxonomy '{$destination_taxonomy}' for {$post_count} {$post_plural}." );
+		WP_CLI::success( "Migrated the term '{$term->slug}' from taxonomy '{$tax->name}' to taxonomy '{$destination_taxonomy}' for {$post_count} {$post_plural}." );
 	}
 
 	private function maybe_make_child() {
diff --git a/src/Term_Meta_Command.php b/src/Term_Meta_Command.php
index f751b6eb..29d2ed24 100644
--- a/src/Term_Meta_Command.php
+++ b/src/Term_Meta_Command.php
@@ -29,11 +29,11 @@ class Term_Meta_Command extends CommandWithMeta {
 	/**
 	 * Check that the term ID exists
 	 *
-	 * @param int
+	 * @param int $object_id
 	 */
 	protected function check_object_id( $object_id ) {
 		$term = get_term( $object_id );
-		if ( ! $term ) {
+		if ( ! $term || is_wp_error( $term ) ) {
 			WP_CLI::error( "Could not find the term with ID {$object_id}." );
 		}
 		return $term->term_id;
@@ -52,7 +52,7 @@ protected function check_object_id( $object_id ) {
 	 *                           value for the specified metadata key, no change
 	 *                           will be made.
 	 *
-	 * @return int|false The meta ID on success, false on failure.
+	 * @return int|false|WP_Error The meta ID on success, false on failure, WP_Error when term_id is ambiguous between taxonomies.
 	 */
 	protected function add_metadata( $object_id, $meta_key, $meta_value, $unique = false ) {
 		return add_term_meta( $object_id, $meta_key, $meta_value, $unique );
@@ -69,8 +69,8 @@ protected function add_metadata( $object_id, $meta_key, $meta_value, $unique = f
 	 *                           metadata entries with the specified value.
 	 *                           Otherwise, update all entries.
 	 *
-	 * @return int|bool Meta ID if the key didn't exist, true on successful
-	 *                  update, false on failure.
+	 * @return int|bool|WP_Error Meta ID if the key didn't exist, true on successful
+	 *                  update, false on failure, WP_Error when term_id is ambiguous between taxonomies.
 	 */
 	protected function update_metadata( $object_id, $meta_key, $meta_value, $prev_value = '' ) {
 		return update_term_meta( $object_id, $meta_key, $meta_value, $prev_value );
diff --git a/src/User_Application_Password_Command.php b/src/User_Application_Password_Command.php
index 89cb4ea9..0dffef71 100644
--- a/src/User_Application_Password_Command.php
+++ b/src/User_Application_Password_Command.php
@@ -163,8 +163,8 @@ public function list_( $args, $assoc_args ) {
 			static function ( $a, $b ) use ( $orderby, $order ) {
 				// Sort array.
 				return 'asc' === $order
-					? $a[ $orderby ] > $b[ $orderby ]
-					: $a[ $orderby ] < $b[ $orderby ];
+					? $a[ $orderby ] <=> $b[ $orderby ]
+					: $b[ $orderby ] <=> $a[ $orderby ];
 			}
 		);
 
@@ -315,8 +315,15 @@ public function get( $args, $assoc_args ) {
 	public function create( $args, $assoc_args ) {
 		$args = $this->replace_login_with_user_id( $args );
 
+		/**
+		 * @var string $user_id
+		 * @var string $app_name
+		 */
 		list( $user_id, $app_name ) = $args;
 
+		/**
+		 * @var string $app_id
+		 */
 		$app_id = Utils\get_flag_value( $assoc_args, 'app-id', '' );
 
 		$arguments = [
@@ -324,7 +331,7 @@ public function create( $args, $assoc_args ) {
 			'app_id' => $app_id,
 		];
 
-		$result = WP_Application_Passwords::create_new_application_password( $user_id, $arguments );
+		$result = WP_Application_Passwords::create_new_application_password( (int) $user_id, $arguments );
 
 		if ( $result instanceof WP_Error ) {
 			WP_CLI::error( $result );
diff --git a/src/User_Command.php b/src/User_Command.php
index 5bad384c..ae6a9e80 100644
--- a/src/User_Command.php
+++ b/src/User_Command.php
@@ -31,6 +31,8 @@
  *     Success: Removed user 123 from http://example.com.
  *
  * @package wp-cli
+ *
+ * @phpstan-import-type UserSite from Site_Command
  */
 class User_Command extends CommandWithDBObject {
 
@@ -152,6 +154,8 @@ public function list_( $args, $assoc_args ) {
 
 		$formatter = $this->get_formatter( $assoc_args );
 
+		// To be fixed in wp-cli/wp-cli.
+		// @phpstan-ignore property.notFound
 		if ( in_array( $formatter->format, [ 'ids', 'count' ], true ) ) {
 			$assoc_args['fields'] = 'ids';
 		} else {
@@ -184,8 +188,14 @@ function ( $user ) {
 						return $user;
 					}
 
+					/**
+					 * @var \WP_User $user
+					 */
+
+					// @phpstan-ignore assign.propertyType
 					$user->roles = implode( ',', $user->roles );
-					$user->url   = get_author_posts_url( $user->ID, $user->user_nicename );
+					// @phpstan-ignore property.notFound
+					$user->url = get_author_posts_url( $user->ID, $user->user_nicename );
 					return $user;
 				}
 			);
@@ -273,8 +283,13 @@ public function get( $args, $assoc_args ) {
 	 *     $ wp user delete $(wp user list --role=contributor --field=ID | head -n 100)
 	 */
 	public function delete( $args, $assoc_args ) {
-		$network  = Utils\get_flag_value( $assoc_args, 'network' ) && is_multisite();
+		$network = Utils\get_flag_value( $assoc_args, 'network' ) && is_multisite();
+
+		/**
+		 * @var string|null $reassign
+		 */
 		$reassign = Utils\get_flag_value( $assoc_args, 'reassign' );
+		$reassign = (int) $reassign;
 
 		if ( $network && $reassign ) {
 			WP_CLI::error( 'Reassigning content to a different user is not supported on multisite.' );
@@ -434,7 +449,7 @@ public function create( $args, $assoc_args ) {
 
 		if ( is_multisite() ) {
 			$result = wpmu_validate_user_signup( $user->user_login, $user->user_email );
-			if ( is_wp_error( $result['errors'] ) && ! empty( $result['errors']->errors ) ) {
+			if ( ! empty( $result['errors']->errors ) ) {
 				WP_CLI::error( $result['errors'] );
 			}
 			$user_id = wpmu_create_user( $user->user_login, $user->user_pass, $user->user_email );
@@ -465,7 +480,7 @@ public function create( $args, $assoc_args ) {
 		}
 
 		if ( Utils\get_flag_value( $assoc_args, 'porcelain' ) ) {
-			WP_CLI::line( $user_id );
+			WP_CLI::line( (string) $user_id );
 		} else {
 			WP_CLI::success( "Created user {$user_id}." );
 			if ( isset( $generated_pass ) ) {
@@ -637,7 +652,7 @@ public function generate( $args, $assoc_args ) {
 				]
 			);
 
-			if ( false === $role ) {
+			if ( false === $role && ! is_wp_error( $user_id ) ) {
 				delete_user_option( $user_id, 'capabilities' );
 				delete_user_option( $user_id, 'user_level' );
 			}
@@ -645,7 +660,10 @@ public function generate( $args, $assoc_args ) {
 			if ( 'progress' === $format ) {
 				$notify->tick();
 			} elseif ( 'ids' === $format ) {
-				echo $user_id;
+				if ( ! is_wp_error( $user_id ) ) {
+					echo $user_id;
+				}
+
 				if ( $index < $limit - 1 ) {
 					echo ' ';
 				}
@@ -710,7 +728,7 @@ public function exists( $args ) {
 	public function set_role( $args, $assoc_args ) {
 		$user = $this->fetcher->get_check( $args[0] );
 
-		$role = Utils\get_flag_value( $args, 1, get_option( 'default_role' ) );
+		$role = $args[1] ?? get_option( 'default_role' );
 
 		self::validate_role( $role );
 
@@ -881,6 +899,9 @@ public function add_cap( $args, $assoc_args ) {
 	 * @subcommand remove-cap
 	 */
 	public function remove_cap( $args, $assoc_args ) {
+		/**
+		 * @var \WP_User $user
+		 */
 		$user = $this->fetcher->get_check( $args[0] );
 		if ( $user ) {
 			$cap = $args[1];
@@ -966,7 +987,9 @@ public function list_caps( $args, $assoc_args ) {
 				}
 				break;
 			case 'user':
-				// Get the user's capabilities
+				/**
+				 * @var array<string, int> $user_capabilities
+				 */
 				$user_capabilities = get_user_meta( $user->ID, 'wp_capabilities', true );
 
 				// Loop through each capability and only return the non-inherited ones
@@ -977,7 +1000,9 @@ public function list_caps( $args, $assoc_args ) {
 				}
 				break;
 			case 'role':
-				// Get the user's capabilities
+				/**
+				 * @var array<string, int> $user_capabilities
+				 */
 				$user_capabilities = get_user_meta( $user->ID, 'wp_capabilities', true );
 
 				// Loop through each capability and only return the inherited ones (including the role name)
@@ -1076,6 +1101,10 @@ public function import_csv( $args, $assoc_args ) {
 			$file_object->setFlags( SplFileObject::READ_CSV );
 			$csv_data = [];
 			$indexes  = [];
+
+			/**
+			 * @var string[] $line
+			 */
 			foreach ( $file_object as $line ) {
 				if ( empty( $line[0] ) ) {
 					continue;
@@ -1086,6 +1115,11 @@ public function import_csv( $args, $assoc_args ) {
 					continue;
 				}
 
+				/**
+				 * @var array<string, string> $data
+				 */
+				$data = [];
+
 				foreach ( $indexes as $n => $key ) {
 					$data[ $key ] = $line[ $n ];
 				}
@@ -1096,6 +1130,9 @@ public function import_csv( $args, $assoc_args ) {
 			$csv_data = new CsvIterator( $filename );
 		}
 
+		/**
+		 * @var array{ID: string, role: string, roles: string, user_pass: string, user_registered: string, display_name: string|false, user_login: string, user_email: string} $new_user
+		 */
 		foreach ( $csv_data as $new_user ) {
 			$defaults = [
 				'role'            => get_option( 'default_role' ),
@@ -1151,13 +1188,18 @@ public function import_csv( $args, $assoc_args ) {
 					WP_CLI::log( "{$existing_user->user_login} added as {$new_user['role']}." );
 				}
 
+				if ( is_wp_error( $user_id ) ) {
+					WP_CLI::warning( $user_id );
+					continue;
+				}
+
 				// Create the user
 			} else {
 				unset( $new_user['ID'] ); // Unset else it will just return the ID
 
 				if ( is_multisite() ) {
 					$result = wpmu_validate_user_signup( $new_user['user_login'], $new_user['user_email'] );
-					if ( is_wp_error( $result['errors'] ) && ! empty( $result['errors']->errors ) ) {
+					if ( ! empty( $result['errors']->errors ) ) {
 						WP_CLI::warning( $result['errors'] );
 						continue;
 					}
@@ -1176,22 +1218,24 @@ public function import_csv( $args, $assoc_args ) {
 					$user_id = wp_insert_user( $new_user );
 				}
 
+				if ( is_wp_error( $user_id ) ) {
+					WP_CLI::warning( $user_id );
+					continue;
+				}
+
 				if ( Utils\get_flag_value( $assoc_args, 'send-email' ) ) {
 					self::wp_new_user_notification( $user_id, $new_user['user_pass'] );
 				}
 			}
 
-			if ( is_wp_error( $user_id ) ) {
-				WP_CLI::warning( $user_id );
-				continue;
-
-			}
-
 			if ( false === $new_user['role'] ) {
 				delete_user_option( $user_id, 'capabilities' );
 				delete_user_option( $user_id, 'user_level' );
 			}
 
+			/**
+			 * @var \WP_User $user
+			 */
 			$user = get_user_by( 'id', $user_id );
 			foreach ( $secondary_roles as $secondary_role ) {
 				$user->add_role( $secondary_role );
@@ -1256,7 +1300,7 @@ public function import_csv( $args, $assoc_args ) {
 	 */
 	public function reset_password( $args, $assoc_args ) {
 		$porcelain     = Utils\get_flag_value( $assoc_args, 'porcelain' );
-		$skip_email    = Utils\get_flag_value( $assoc_args, 'skip-email' );
+		$skip_email    = (bool) Utils\get_flag_value( $assoc_args, 'skip-email' );
 		$show_new_pass = Utils\get_flag_value( $assoc_args, 'show-password' );
 
 		if ( $skip_email ) {
@@ -1313,24 +1357,13 @@ private static function validate_role( $role, $warn_user_only = false ) {
 	}
 
 	/**
-	 * Accommodates three different behaviors for wp_new_user_notification()
-	 * - 4.3.1 and above: expect second argument to be deprecated
-	 * - 4.3: Second argument was repurposed as $notify
-	 * - Below 4.3: Send the password in the notification
+	 * Wrapper around wp_new_user_notification().
 	 *
-	 * @param string $user_id
-	 * @param string $password
+	 * @param string|int $user_id
+	 * @param mixed $password
 	 */
 	public static function wp_new_user_notification( $user_id, $password ) {
-		if ( Utils\wp_version_compare( '4.3.1', '>=' ) ) {
-			wp_new_user_notification( $user_id, null, 'both' );
-		} elseif ( Utils\wp_version_compare( '4.3', '>=' ) ) {
-			// phpcs:ignore WordPress.WP.DeprecatedParameters.Wp_new_user_notificationParam2Found -- Only called in valid conditions.
-			wp_new_user_notification( $user_id, 'both' );
-		} else {
-			// phpcs:ignore WordPress.WP.DeprecatedParameters.Wp_new_user_notificationParam2Found -- Only called in valid conditions.
-			wp_new_user_notification( $user_id, $password );
-		}
+		wp_new_user_notification( (int) $user_id, null, 'both' );
 	}
 
 	/**
@@ -1381,6 +1414,9 @@ private function update_msuser_status( $user_ids, $pref, $value ) {
 			WP_CLI::error( 'This is not a multisite installation.' );
 		}
 
+		$action = 'updated';
+		$verb   = 'update';
+
 		if ( 'spam' === $pref ) {
 			$action = (int) $value ? 'marked as spam' : 'removed from spam';
 			$verb   = (int) $value ? 'spam' : 'unspam';
@@ -1409,6 +1445,10 @@ private function update_msuser_status( $user_ids, $pref, $value ) {
 			}
 
 			// Make that user's blog as spam too.
+
+			/**
+			 * @phpstan-var UserSite[] $blogs
+			 */
 			$blogs = (array) get_blogs_of_user( $user_id, true );
 			foreach ( $blogs as $details ) {
 				// Only mark site as spam if not main site.
diff --git a/src/User_Meta_Command.php b/src/User_Meta_Command.php
index c5ee8033..ccee72cb 100644
--- a/src/User_Meta_Command.php
+++ b/src/User_Meta_Command.php
@@ -316,7 +316,7 @@ protected function delete_metadata( $object_id, $meta_key, $meta_value = '' ) {
 	 * Replaces user_login value with user ID
 	 * user meta is a special case that also supports user_login
 	 *
-	 * @param array
+	 * @param array $args
 	 * @return array
 	 */
 	private function replace_login_with_user_id( $args ) {
diff --git a/src/User_Session_Command.php b/src/User_Session_Command.php
index d5b9e195..3949d6f9 100644
--- a/src/User_Session_Command.php
+++ b/src/User_Session_Command.php
@@ -71,8 +71,8 @@ public function __construct() {
 	 */
 	public function destroy( $args, $assoc_args ) {
 		$user    = $this->fetcher->get_check( $args[0] );
-		$token   = Utils\get_flag_value( $args, 1, null );
-		$all     = Utils\get_flag_value( $assoc_args, 'all', false );
+		$token   = $args[1] ?? null;
+		$all     = (bool) Utils\get_flag_value( $assoc_args, 'all', false );
 		$manager = WP_Session_Tokens::get_instance( $user->ID );
 
 		if ( $token && $all ) {
@@ -174,6 +174,10 @@ protected function get_all_sessions( WP_Session_Tokens $manager ) {
 		// Make the private session data accessible to WP-CLI
 		$get_sessions = new ReflectionMethod( $manager, 'get_sessions' );
 		$get_sessions->setAccessible( true );
+
+		/**
+		 * @var array<array{token: string|int, login_time: string, login: int, expiration_time: string, expiration: int}> $sessions
+		 */
 		$sessions = $get_sessions->invoke( $manager );
 
 		array_walk(
diff --git a/src/WP_CLI/CommandWithDBObject.php b/src/WP_CLI/CommandWithDBObject.php
index cb3215bb..767a0bb2 100644
--- a/src/WP_CLI/CommandWithDBObject.php
+++ b/src/WP_CLI/CommandWithDBObject.php
@@ -33,9 +33,9 @@ abstract class CommandWithDBObject extends WP_CLI_Command {
 	 * Create a given database object.
 	 * Exits with status.
 	 *
-	 * @param array $args Arguments passed to command. Generally unused.
-	 * @param array $assoc_args Parameters passed to command to be passed to callback.
-	 * @param string $callback Function used to create object.
+	 * @param array    $args       Arguments passed to command. Generally unused.
+	 * @param array    $assoc_args Parameters passed to command to be passed to callback.
+	 * @param callable $callback   Function used to create object.
 	 */
 	protected function _create( $args, $assoc_args, $callback ) {
 		unset( $assoc_args[ $this->obj_id_key ] );
@@ -57,9 +57,9 @@ protected function _create( $args, $assoc_args, $callback ) {
 	 * Update a given database object.
 	 * Exits with status.
 	 *
-	 * @param array $args Collection of one or more object ids to update.
-	 * @param array $assoc_args Fields => values to update on each object.
-	 * @param string $callback Function used to update object.
+	 * @param array    $args       Collection of one or more object ids to update.
+	 * @param array    $assoc_args Fields => values to update on each object.
+	 * @param callable $callback   Function used to update object.
 	 */
 	protected function _update( $args, $assoc_args, $callback ) {
 		$status = 0;
@@ -184,17 +184,4 @@ protected function get_formatter( &$assoc_args ) {
 		}
 		return new Formatter( $assoc_args, $fields, $this->obj_type );
 	}
-
-	/**
-	 * Given a callback, display the URL for one or more objects.
-	 *
-	 * @param array $args One or more object references.
-	 * @param string $callback Function to get URL for the object.
-	 */
-	protected function _url( $args, $callback ) {
-		foreach ( $args as $obj_id ) {
-			$object = $this->fetcher->get_check( $obj_id );
-			WP_CLI::line( $callback( $object->{$this->obj_id_key} ) );
-		}
-	}
 }
diff --git a/src/WP_CLI/CommandWithMeta.php b/src/WP_CLI/CommandWithMeta.php
index 984f66c1..23cc5baf 100644
--- a/src/WP_CLI/CommandWithMeta.php
+++ b/src/WP_CLI/CommandWithMeta.php
@@ -91,7 +91,7 @@ public function list_( $args, $assoc_args ) {
 			foreach ( $values as $item_value ) {
 
 				if ( Utils\get_flag_value( $assoc_args, 'unserialize' ) ) {
-					$item_value = maybe_unserialize( $item_value );
+					$item_value = maybe_unserialize( (string) $item_value );
 				}
 
 				$items[] = (object) [
@@ -112,8 +112,8 @@ public function list_( $args, $assoc_args ) {
 				function ( $a, $b ) use ( $orderby, $order ) {
 					// Sort array.
 					return 'asc' === $order
-						? $a->$orderby > $b->$orderby
-						: $a->$orderby < $b->$orderby;
+						? $a->$orderby <=> $b->$orderby
+						: $b->$orderby <=> $a->$orderby;
 				}
 			);
 
@@ -159,7 +159,7 @@ public function get( $args, $assoc_args ) {
 		list( $object_id, $meta_key ) = $args;
 
 		$object_id = $this->check_object_id( $object_id );
-		$single    = Utils\get_flag_value( $assoc_args, 'single', true );
+		$single    = (bool) Utils\get_flag_value( $assoc_args, 'single', true );
 
 		$value = $this->get_metadata( $object_id, $meta_key, $single );
 
@@ -504,6 +504,8 @@ protected function update_metadata( $object_id, $meta_key, $meta_value, $prev_va
 	 *                          specified.
 	 *
 	 * @return mixed Single metadata value, or array of values.
+	 *
+	 * @phpstan-return ($single is true ? string : array<string>)
 	 */
 	protected function get_metadata( $object_id, $meta_key = '', $single = false ) {
 		return get_metadata( $this->meta_type, $object_id, $meta_key, $single );
@@ -545,7 +547,7 @@ private function get_fields() {
 	/**
 	 * Check that the object ID exists
 	 *
-	 * @param int
+	 * @param int $object_id
 	 */
 	protected function check_object_id( $object_id ) {
 		// Needs to be set in subclass
diff --git a/src/WP_CLI/CommandWithTerms.php b/src/WP_CLI/CommandWithTerms.php
index 1fa4562f..0e4f9c4d 100644
--- a/src/WP_CLI/CommandWithTerms.php
+++ b/src/WP_CLI/CommandWithTerms.php
@@ -103,6 +103,9 @@ public function list_( $args, $assoc_args ) {
 			$taxonomy_args['fields'] = 'ids';
 		}
 
+		/**
+		 * @var \WP_Term[] $items
+		 */
 		$items = wp_get_object_terms( $object_id, $taxonomy_names, $taxonomy_args );
 
 		$formatter = $this->get_formatter( $assoc_args );
@@ -145,12 +148,15 @@ public function remove( $args, $assoc_args ) {
 
 		$this->taxonomy_exists( $taxonomy );
 
+		/**
+		 * @var string|null $field
+		 */
 		$field = Utils\get_flag_value( $assoc_args, 'by' );
 		if ( $field ) {
 			$terms = $this->prepare_terms( $field, $terms, $taxonomy );
 		}
 
-		if ( Utils\get_flag_value( $assoc_args, 'all' ) ) {
+		if ( (bool) Utils\get_flag_value( $assoc_args, 'all' ) ) {
 
 			// No need to specify terms while removing all terms.
 			if ( $terms ) {
@@ -164,7 +170,12 @@ public function remove( $args, $assoc_args ) {
 			if ( 'category' === $taxonomy ) {
 
 				// Set default category to post.
-				$default_category = (int) get_option( 'default_category' );
+
+				/**
+				 * @var string $default_category
+				 */
+				$default_category = get_option( 'default_category' );
+				$default_category = (int) $default_category;
 				$default_category = ( ! empty( $default_category ) ) ? $default_category : 1;
 				$default_category = wp_set_object_terms( $object_id, [ $default_category ], $taxonomy, true );
 
@@ -235,6 +246,9 @@ public function add( $args, $assoc_args ) {
 
 		$this->taxonomy_exists( $taxonomy );
 
+		/**
+		 * @var string|null $field
+		 */
 		$field = Utils\get_flag_value( $assoc_args, 'by' );
 		if ( $field ) {
 			$terms = $this->prepare_terms( $field, $terms, $taxonomy );
@@ -283,6 +297,9 @@ public function set( $args, $assoc_args ) {
 
 		$this->taxonomy_exists( $taxonomy );
 
+		/**
+		 * @var string|null $field
+		 */
 		$field = Utils\get_flag_value( $assoc_args, 'by' );
 		if ( $field ) {
 			$terms = $this->prepare_terms( $field, $terms, $taxonomy );