diff --git a/src/wp-includes/comment.php b/src/wp-includes/comment.php
index 4b192ea02e..304536b9d2 100644
--- a/src/wp-includes/comment.php
+++ b/src/wp-includes/comment.php
@@ -2639,10 +2639,20 @@ function do_all_pings() {
 		pingback( $ping->post_content, $ping->ID );
 	}
 
-	// Do Enclosures
-	while ( $enclosure = $wpdb->get_row( "SELECT ID, post_content, meta_id FROM {$wpdb->posts}, {$wpdb->postmeta} WHERE {$wpdb->posts}.ID = {$wpdb->postmeta}.post_id AND {$wpdb->postmeta}.meta_key = '_encloseme' LIMIT 1" ) ) {
-		delete_metadata_by_mid( 'post', $enclosure->meta_id );
-		do_enclose( $enclosure->post_content, $enclosure->ID );
+	// Do enclosures.
+	$enclosures = get_posts(
+		array(
+			'post_type'        => get_post_types(),
+			'suppress_filters' => false,
+			'nopaging'         => true,
+			'meta_key'         => '_encloseme',
+			'fields'           => 'ids',
+		)
+	);
+
+	foreach ( $enclosure as $enclosure ) {
+		delete_post_meta( $enclosure, '_encloseme' );
+		do_enclose( null, $enclosure->ID );
 	}
 
 	// Do Trackbacks
diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 035347e1ed..97d8941478 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -799,27 +799,39 @@ function wp_extract_urls( $content ) {
  * pingbacks and trackbacks.
  *
  * @since 1.5.0
+ * @since 5.3.0 The `$content` parameter was made optional, and the `$post` parameter was
+ *              updated to accept a post ID or a WP_Post object.
  *
  * @global wpdb $wpdb WordPress database abstraction object.
  *
- * @param string $content Post Content.
- * @param int    $post_ID Post ID.
+ * @param string         $content Post content. If `null`, the `post_content` field from `$post` is used.
+ * @param int|WP_Post    $post    Post ID or post object.
+ * @return null|bool Returns false if post is not found.
  */
-function do_enclose( $content, $post_ID ) {
+function do_enclose( $content = null, $post ) {
 	global $wpdb;
 
 	//TODO: Tidy this ghetto code up and make the debug code optional
 	include_once( ABSPATH . WPINC . '/class-IXR.php' );
 
+	$post = get_post( $post );
+	if ( ! $post ) {
+		return false;
+	}
+
+	if ( null === $content ) {
+		$content = $post->post_content;
+	}
+
 	$post_links = array();
 
-	$pung = get_enclosed( $post_ID );
+	$pung = get_enclosed( $post->ID );
 
 	$post_links_temp = wp_extract_urls( $content );
 
 	foreach ( $pung as $link_test ) {
 		if ( ! in_array( $link_test, $post_links_temp ) ) { // link no longer in post
-			$mids = $wpdb->get_col( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = 'enclosure' AND meta_value LIKE %s", $post_ID, $wpdb->esc_like( $link_test ) . '%' ) );
+			$mids = $wpdb->get_col( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = 'enclosure' AND meta_value LIKE %s", $post->ID, $wpdb->esc_like( $link_test ) . '%' ) );
 			foreach ( $mids as $mid ) {
 				delete_metadata_by_mid( 'post', $mid );
 			}
@@ -851,10 +863,10 @@ function do_enclose( $content, $post_ID ) {
 	 * @param array $post_links An array of enclosure links.
 	 * @param int   $post_ID    Post ID.
 	 */
-	$post_links = apply_filters( 'enclosure_links', $post_links, $post_ID );
+	$post_links = apply_filters( 'enclosure_links', $post_links, $post->ID );
 
 	foreach ( (array) $post_links as $url ) {
-		if ( $url != '' && ! $wpdb->get_var( $wpdb->prepare( "SELECT post_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = 'enclosure' AND meta_value LIKE %s", $post_ID, $wpdb->esc_like( $url ) . '%' ) ) ) {
+		if ( $url != '' && ! $wpdb->get_var( $wpdb->prepare( "SELECT post_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = 'enclosure' AND meta_value LIKE %s", $post->ID, $wpdb->esc_like( $url ) . '%' ) ) ) {
 
 			$headers = wp_get_http_headers( $url );
 			if ( $headers ) {
@@ -878,7 +890,7 @@ function do_enclose( $content, $post_ID ) {
 				}
 
 				if ( in_array( substr( $type, 0, strpos( $type, '/' ) ), $allowed_types ) ) {
-					add_post_meta( $post_ID, 'enclosure', "$url\n$len\n$mime\n" );
+					add_post_meta( $post->ID, 'enclosure', "$url\n$len\n$mime\n" );
 				}
 			}
 		}
diff --git a/tests/phpunit/tests/functions/doEnclose.php b/tests/phpunit/tests/functions/doEnclose.php
new file mode 100644
index 0000000000..196fe0c30a
--- /dev/null
+++ b/tests/phpunit/tests/functions/doEnclose.php
@@ -0,0 +1,305 @@
+<?php
+/**
+ * Test cases for the `do_enclose()` function.
+ *
+ * @package WordPress\UnitTests
+ *
+ * @since 5.3.0
+ */
+
+/**
+ * Tests_Functions_DoEnclose class.
+ *
+ * @group functions.php
+ * @group post
+ * @covers do_enclose
+ *
+ * @since 5.3.0
+ */
+class Tests_Functions_DoEnclose extends WP_UnitTestCase {
+
+	/**
+	 * Setup before each test method.
+	 *
+	 * @since 5.3.0
+	 */
+	public function setUp() {
+		parent::setUp();
+		add_filter( 'pre_http_request', array( $this, 'fake_http_request' ), 10, 3 );
+	}
+
+	/**
+	 * Cleanup after each test method.
+	 *
+	 * @since 5.3.0
+	 */
+	public function tearDown() {
+		parent::tearDown();
+		remove_filter( 'pre_http_request', array( $this, 'fake_http_request' ) );
+	}
+
+	/**
+	 * Test the function with an explicit content input.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @dataProvider data_test_do_enclose
+	 */
+	public function test_function_with_explicit_content_input( $content, $expected ) {
+		$post_id = self::factory()->post->create();
+
+		do_enclose( $content, $post_id );
+
+		$actual = $this->get_enclosed_by_post_id( $post_id );
+		$this->assertSame( $expected, $actual );
+	}
+
+	/**
+	 * Test the function with an implicit content input.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @dataProvider data_test_do_enclose
+	 */
+	public function test_function_with_implicit_content_input( $content, $expected ) {
+		$post_id = self::factory()->post->create(
+			array(
+				'post_content' => $content,
+			)
+		);
+
+		do_enclose( null, $post_id );
+
+		$actual = $this->get_enclosed_by_post_id( $post_id );
+		$this->assertSame( $expected, $actual );
+	}
+
+	/**
+	 * Dataprovider for `test_function_with_explicit_content_input()`
+	 * and `test_function_with_implicit_content_input()`.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @return array {
+	 *     @type array {
+	 *         @type string Post content.
+	 *         @type string Expected values.
+	 *     }
+	 * }
+	 */
+	public function data_test_do_enclose() {
+		return array(
+			'null'                  => array(
+				'content'  => null,
+				'expected' => '',
+			),
+			'empty'                 => array(
+				'content'  => '',
+				'expected' => '',
+			),
+			'single-bare-movie'     => array(
+				'content'  => 'movie.mp4',
+				'expected' => '',
+			),
+			'single-bare-audio'     => array(
+				'content'  => 'audio.ogg',
+				'expected' => '',
+			),
+			'single-relative-movie' => array(
+				'content'  => '/movie.mp4',
+				'expected' => "/movie.mp4\n123\nvideo/mp4\n",
+			),
+			'single-relative-audio' => array(
+				'content'  => '/audio.ogg',
+				'expected' => "/audio.ogg\n321\naudio/ogg\n",
+			),
+			'single-unknown'        => array(
+				'content'  => 'https://example.com/wp-content/uploads/2018/06/file.unknown',
+				'expected' => '',
+			),
+			'single-movie'          => array(
+				'content'  => 'https://example.com/wp-content/uploads/2018/06/movie.mp4',
+				'expected' => "https://example.com/wp-content/uploads/2018/06/movie.mp4\n123\nvideo/mp4\n",
+			),
+			'single-audio'          => array(
+				'content'  => 'https://example.com/wp-content/uploads/2018/06/audio.ogg',
+				'expected' => "https://example.com/wp-content/uploads/2018/06/audio.ogg\n321\naudio/ogg\n",
+			),
+			'single-movie-query'    => array(
+				'content'  => 'https://example.com/wp-content/uploads/2018/06/movie.mp4?test=1',
+				'expected' => "https://example.com/wp-content/uploads/2018/06/movie.mp4?test=1\n123\nvideo/mp4\n",
+			),
+			'multi'                 => array(
+				'content'  => "https://example.com/wp-content/uploads/2018/06/audio.ogg\n" .
+								'https://example.com/wp-content/uploads/2018/06/movie.mp4',
+				'expected' => "https://example.com/wp-content/uploads/2018/06/audio.ogg\n321\naudio/ogg\n" .
+								"https://example.com/wp-content/uploads/2018/06/movie.mp4\n123\nvideo/mp4\n",
+			),
+		);
+	}
+
+	/**
+	 * The function should return false when the post ID input is invalid.
+	 *
+	 * @since 5.3.0
+	 */
+	public function test_function_should_return_false_when_invalid_post_id() {
+		$post_id = null;
+		$result  = do_enclose( null, $post_id );
+		$this->assertFalse( $result );
+	}
+
+	/**
+	 * The function should delete an enclosed link when it's no longer in the post content.
+	 *
+	 * @since 5.3.0
+	 */
+	public function test_function_should_delete_enclosed_link_when_no_longer_in_post_content() {
+		$data = $this->data_test_do_enclose();
+
+		// Create a post with a single movie link.
+		$post_id = self::factory()->post->create(
+			array(
+				'post_content' => $data['single-movie']['content'],
+			)
+		);
+
+		do_enclose( null, $post_id );
+
+		$actual = $this->get_enclosed_by_post_id( $post_id );
+		$this->assertSame( $data['single-movie']['expected'], $actual );
+
+		// Replace the movie link with an audio link.
+		wp_update_post(
+			array(
+				'ID'           => $post_id,
+				'post_content' => $data['single-audio']['content'],
+			)
+		);
+
+		do_enclose( null, $post_id );
+
+		$actual = $this->get_enclosed_by_post_id( $post_id );
+		$this->assertSame( $data['single-audio']['expected'], $actual );
+	}
+
+	/**
+	 * The function should support a post object input.
+	 *
+	 * @since 5.3.0
+	 */
+	public function test_function_should_support_post_object_input() {
+		$data = $this->data_test_do_enclose();
+
+		$post_object = self::factory()->post->create_and_get(
+			array(
+				'post_content' => $data['multi']['content'],
+			)
+		);
+
+		do_enclose( null, $post_object );
+
+		$actual = $this->get_enclosed_by_post_id( $post_object->ID );
+		$this->assertSame( $data['multi']['expected'], $actual );
+	}
+
+	/**
+	 * The enclosure links should be filterable with the `enclosure_links` filter.
+	 *
+	 * @since 5.3.0
+	 */
+	public function test_function_enclosure_links_should_be_filterable() {
+		$data = $this->data_test_do_enclose();
+
+		$post_id = self::factory()->post->create(
+			array(
+				'post_content' => $data['multi']['content'],
+			)
+		);
+
+		add_filter( 'enclosure_links', array( $this, 'filter_enclosure_links' ), 10, 2 );
+		do_enclose( null, $post_id );
+		remove_filter( 'enclosure_links', array( $this, 'filter_enclosure_links' ) );
+
+		$actual   = $this->get_enclosed_by_post_id( $post_id );
+		$expected = str_replace( 'example.org', sprintf( 'example-%d.org', $post_id ), $data['multi']['expected'] );
+		$this->assertSame( $expected, $actual );
+	}
+
+	/**
+	 * A callback to filter the list of enclosure links.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param  array $post_links An array of enclosure links.
+	 * @param  int   $post_id    Post ID.
+	 * @return array $post_links An array of enclosure links.
+	 */
+	public function filter_enclosure_links( $enclosure_links, $post_id ) {
+		// Replace the link host to contain the post ID, to test both filter input arguments.
+		foreach ( $enclosure_links as &$link ) {
+			$link = str_replace( 'example.org', sprintf( 'example-%d.org', $post_id ), $link );
+		}
+		return $enclosure_links;
+	}
+
+	/**
+	 * Helper function to get all enclosure data for a given post.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param  int    $post_id Post ID.
+	 * @return string          All enclosure data for the given post.
+	 */
+	protected function get_enclosed_by_post_id( $post_id ) {
+		return join( (array) get_post_meta( $post_id, 'enclosure', false ), '' );
+	}
+
+	/**
+	 * Fake the HTTP request response.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param bool   $false     False.
+	 * @param array  $arguments Request arguments.
+	 * @param string $url       Request URL.
+	 *
+	 * @return array            Header.
+	 */
+	public function fake_http_request( $false, $arguments, $url ) {
+
+		// Video and audio headers.
+		$fake_headers = array(
+			'mp4' => array(
+				'headers' => array(
+					'content-length' => 123,
+					'content-type'   => 'video/mp4',
+				),
+			),
+			'ogg' => array(
+				'headers' => array(
+					'content-length' => 321,
+					'content-type'   => 'audio/ogg',
+				),
+			),
+		);
+
+		$path = parse_url( $url, PHP_URL_PATH );
+
+		if ( false !== $path ) {
+			$extension = pathinfo( $path, PATHINFO_EXTENSION );
+			if ( isset( $fake_headers[ $extension ] ) ) {
+				return $fake_headers[ $extension ];
+			}
+		}
+
+		// Fallback header.
+		return array(
+			'headers' => array(
+				'content-length' => 0,
+				'content-type'   => '',
+			),
+		);
+	}
+
+}