wp_rel_nofollow() WordPress Function

function wp_rel_nofollow( $text ) {
	// This is a pre-save filter, so text is already escaped.
	$text = stripslashes( $text );
	$text = preg_replace_callback(
		'|<a (.+?)>|i',
		static function( $matches ) {
			return wp_rel_callback( $matches, 'nofollow' );
		},
		$text
	);
	return wp_slash( $text );
}
Uses	Description
wp-includes/formatting.php:wp_rel_callback()	Callback to add a rel attribute to HTML A element.
wp-includes/formatting.php:wp_slash()	Adds slashes to a string or recursively adds slashes to strings within an array.