Remove Special Characters

[phpcodec]

How can i write a regex that will check for any characters that are not in the list below and return true if any unknown characters are found

 

a-z

A-Z

0-9

_ (under-dash)

- (hypen)

  (space)

[MadTechie]

$text = preg_replace('/[^a-zA-Z0-9_ -]/s', '', $text);

 

or i shorter version

$text= preg_replace('/[^\w\d_ -]/si', '', $text);

 

EDIT: the above is a clean up

heres to match

<?php
if (preg_match('/[^\w\d_ -]/si', $text))
{
echo "found unknown characters";
}
?>

[discomatt]

I believe underscore is already matched in the \w shorthand so you could make it even shorter

[MadTechie]

Doh!... very true

[nrg_alpha]

Depending on locale, \w *might* match additional characters such as à ò ì ù è. Something to consider. Also, \d can match more than simply 0-9 (example:  0¹²³4). However, I'm not sure if this is locale dependent or not.

 

So depending on what string content is being checked, there may be some pitfalls if one is not careful.