Regex remove all but alpha numeric and -_

[coldscooter]

Hi, I would like to remove all chars but alpha numeric and _- from a string.

I have got this so far:

preg_replace('/[^a-zA-Z0-9\s]/', '', $string)

But i don't know how to leave in - and _

Any help would be much appreciated.

[NogDog]

You can just add the underscore directly into the character class. For the hyphen, you can do the same if you make it the very last thing in the class (so that it is not interpreted as indicating a range of characters, or it can be anywhere if you escape it with a back-slash.