Regular expression help needed

[suepahfly]

Hi,

I want to filter a string. Only the characters [A_Z] [0-9] and the +' and-' ( boolean operaters ) are allowd, the rest should be trashed.
But since i'm a total noob on regexp (even after many, reading i still don't get it). I need some help 🙂

[gavwvin]

if(!preg_match("#[A-Za-z0-9-+]+#",$text_to_filter)) {
//show error
}

This checks that $text_to_filter is one or more characters, only A-Z a-z 0-9 or + or -

[Weedpacket]

Simpler regexp:

/[^A-Z0-9+-]/

If that succeeds, then there was an invalid character (gavwin's code will show an error if there weren't any valid characters in the string).

You could also look at [man]strspn[/man] if you want to avoid regexps.