return only normal characters (a-z 0-9) php function using preg_replace

here is a nice simple function that uses preg_replace to clean a string, and make sure it returns only normal characters.

It is another way of cleaning a string, similar to the method i used in Generate Safe File Name in PHP using ereg_replace function.

Not sure really which is better i think one of them may be faster than the other. Please feel free to comment and let me know.

return only normal characters (a-z 0-9) php function using preg_replace