These ones should just be omitted altogether if they are blank. foreach ( array( 'loop', 'autoplay', 'preload' ) as $a ) { if ( empty( $html_atts[ $a ] ) ) { unset( $html_atts[ $a ] ); } } $attr_strings = array(); foreach ( $html_atts as $k => $v ) { $attr_strings[] = $k . '="' . esc_attr( $v ) . '"'; } $html = ''; if ( 'mediaelement' === $library && 1 === $instance ) { $html .= "\n"; } $html .= sprintf( ''; /** * Filters the audio shortcode output. * * @since 3.6.0 * * @param string $html Audio shortcode HTML output. * @param array $atts Array of audio shortcode attributes. * @param string $audio Audio file. * @param int $post_id Post ID. * @param string $library Media library used for the audio shortcode. */ return apply_filters( 'wp_audio_shortcode', $html, $atts, $audio, $post_id, $library ); } add_shortcode( 'audio', 'wp_audio_shortcode' ); /** * Returns a filtered list of supported video formats. * * @since 3.6.0 * * @return string[] List of supported video formats. */ function wp_get_video_extensions() { /** * Filters the list of supported video formats. * * @since 3.6.0 * * @param string[] $extensions An array of supported video formats. Defaults are * 'mp4', 'm4v', 'webm', 'ogv', 'flv'. */ return apply_filters( 'wp_video_extensions', array( 'mp4', 'm4v', 'webm', 'ogv', 'flv' ) ); } /** * Builds the Video shortcode output. * * This implements the functionality of the Video Shortcode for displaying * WordPress mp4s in a post. * * @since 3.6.0 * * @global int $content_width * * @param array $attr { * Attributes of the shortcode. * * @type string $src URL to the source of the video file. Default empty. * @type int $height Height of the video embed in pixels. Default 360. * @type int $width Width of the video embed in pixels. Default $content_width or 640. * @type string $poster The 'poster' attribute for the `