preg_replace_callback alternative of preg_replace

Question

I am currently using

preg_replace('/[^a-zA-Z0-9]+/', '_', $str)

what would be the alternative function using preg_replace_callback?

Answer 1

I did it myself

function url_title($mystr){
	$result = '';
	$result .= preg_replace_callback(
                '/[^a-zA-Z0-9]+/',
                function ($matches) { return '_'; }, 
                $mystr);
						
	return strtolower($result);
}

$mystr = "some string here";
echo url_title($mystr);