rss_enclosure() WordPress Function

function rss_enclosure() {
	if ( post_password_required() ) {
		return;
	}

	foreach ( (array) get_post_custom() as $key => $val ) {
		if ( 'enclosure' === $key ) {
			foreach ( (array) $val as $enc ) {
				$enclosure = explode( "\n", $enc );

				// Only get the first element, e.g. 'audio/mpeg' from 'audio/mpeg mpga mp2 mp3'.
				$t    = preg_split( '/[ \t]/', trim( $enclosure[2] ) );
				$type = $t[0];

				/**
				 * Filters the RSS enclosure HTML link tag for the current post.
				 *
				 * @since 2.2.0
				 *
				 * @param string $html_link_tag The HTML link tag with a URI and other attributes.
				 */
				echo apply_filters( 'rss_enclosure', '<enclosure url="' . esc_url( trim( $enclosure[0] ) ) . '" length="' . absint( trim( $enclosure[1] ) ) . '" type="' . esc_attr( $type ) . '" />' . "\n" );
			}
		}
	}
}
Uses	Description
wp-includes/formatting.php:esc_url()	Checks and cleans a URL.
wp-includes/formatting.php:esc_attr()	Escaping for HTML attributes.
wp-includes/functions.php:absint()	Convert a value to non-negative integer.
wp-includes/plugin.php:apply_filters()	Calls the callback functions that have been added to a filter hook.
wp-includes/feed.php:rss_enclosure	Filters the RSS enclosure HTML link tag for the current post.
wp-includes/post-template.php:post_password_required()	Determines whether the post requires password and whether a correct password has been provided.
wp-includes/post.php:get_post_custom()	Retrieve post meta fields, based on post ID.