translate_smiley() WordPress Function

function translate_smiley( $matches ) {
	global $wpsmiliestrans;

	if ( count( $matches ) == 0 ) {
		return '';
	}

	$smiley = trim( reset( $matches ) );
	$img    = $wpsmiliestrans[ $smiley ];

	$matches    = array();
	$ext        = preg_match( '/\.([^.]+)$/', $img, $matches ) ? strtolower( $matches[1] ) : false;
	$image_exts = array( 'jpg', 'jpeg', 'jpe', 'gif', 'png', 'webp' );

	// Don't convert smilies that aren't images - they're probably emoji.
	if ( ! in_array( $ext, $image_exts, true ) ) {
		return $img;
	}

	/**
	 * Filters the Smiley image URL before it's used in the image element.
	 *
	 * @since 2.9.0
	 *
	 * @param string $smiley_url URL for the smiley image.
	 * @param string $img        Filename for the smiley image.
	 * @param string $site_url   Site URL, as returned by site_url().
	 */
	$src_url = apply_filters( 'smilies_src', includes_url( "images/smilies/$img" ), $img, site_url() );

	return sprintf( '<img src="%s" alt="%s" class="wp-smiley" style="height: 1em; max-height: 1em;" />', esc_url( $src_url ), esc_attr( $smiley ) );
}