A WordPress-centric search engine for devs and theme authors



wp_filter_content_tags ›

Since5.5.0
Deprecatedn/a
› wp_filter_content_tags ( $content, $context = null )
Parameters: (2)
  • (string) $content The HTML content to be filtered.
    Required: Yes
  • (string) $context Optional. Additional context to pass to the filters. Defaults to `current_filter()` when not set.
    Required: No
    Default: null
See:
Returns:
  • (string) Converted content with images modified.
Defined at:
Codex:
Change Log:
  • 5.7.0

Filters specific tags in post content and modifies their markup.

Modifies HTML tags in post content to include new browser and HTML technologies that may not have existed at the time of post creation. These modifications currently include adding srcset, sizes, and loading attributes to img HTML tags, as well as adding loading attributes to iframe HTML tags. Future similar optimizations should be added/expected here.


Related Functions: wp_filter_object_list, wp_filter_post_kses, filter_block_content, wp_filter_nohtml_kses, the_content_rss

Source 

function wp_filter_content_tags( $content, $context = null ) {
	if ( null === $context ) {
		$context = current_filter();
	}

	$add_img_loading_attr    = wp_lazy_loading_enabled( 'img', $context );
	$add_iframe_loading_attr = wp_lazy_loading_enabled( 'iframe', $context );

	if ( ! preg_match_all( '/<(img|iframe)\s[^>]+>/', $content, $matches, PREG_SET_ORDER ) ) {
		return $content;
	}

	// List of the unique `img` tags found in $content.
	$images = array();

	// List of the unique `iframe` tags found in $content.
	$iframes = array();

	foreach ( $matches as $match ) {
		list( $tag, $tag_name ) = $match;

		switch ( $tag_name ) {
			case 'img':
				if ( preg_match( '/wp-image-([0-9]+)/i', $tag, $class_id ) ) {
					$attachment_id = absint( $class_id[1] );

					if ( $attachment_id ) {
						// If exactly the same image tag is used more than once, overwrite it.
						// All identical tags will be replaced later with 'str_replace()'.
						$images[ $tag ] = $attachment_id;
						break;
					}
				}
				$images[ $tag ] = 0;
				break;
			case 'iframe':
				$iframes[ $tag ] = 0;
				break;
		}
	}

	// Reduce the array to unique attachment IDs.
	$attachment_ids = array_unique( array_filter( array_values( $images ) ) );

	if ( count( $attachment_ids ) > 1 ) {
		/*
		 * Warm the object cache with post and meta information for all found
		 * images to avoid making individual database calls.
		 */
		_prime_post_caches( $attachment_ids, false, true );
	}

	foreach ( $images as $image => $attachment_id ) {
		$filtered_image = $image;

		// Add 'width' and 'height' attributes if applicable.
		if ( $attachment_id > 0 && false === strpos( $filtered_image, ' width=' ) && false === strpos( $filtered_image, ' height=' ) ) {
			$filtered_image = wp_img_tag_add_width_and_height_attr( $filtered_image, $context, $attachment_id );
		}

		// Add 'srcset' and 'sizes' attributes if applicable.
		if ( $attachment_id > 0 && false === strpos( $filtered_image, ' srcset=' ) ) {
			$filtered_image = wp_img_tag_add_srcset_and_sizes_attr( $filtered_image, $context, $attachment_id );
		}

		// Add 'loading' attribute if applicable.
		if ( $add_img_loading_attr && false === strpos( $filtered_image, ' loading=' ) ) {
			$filtered_image = wp_img_tag_add_loading_attr( $filtered_image, $context );
		}

		if ( $filtered_image !== $image ) {
			$content = str_replace( $image, $filtered_image, $content );
		}
	}

	foreach ( $iframes as $iframe => $attachment_id ) {
		$filtered_iframe = $iframe;

		// Add 'loading' attribute if applicable.
		if ( $add_iframe_loading_attr && false === strpos( $filtered_iframe, ' loading=' ) ) {
			$filtered_iframe = wp_iframe_tag_add_loading_attr( $filtered_iframe, $context );
		}

		if ( $filtered_iframe !== $iframe ) {
			$content = str_replace( $iframe, $filtered_iframe, $content );
		}
	}

	return $content;
}