Validate characters in a string

[aeboi80]

I have a keyword string which I need to verify only contains the following character set

0123456789abcdefghijklmnopqrstuvwxyz

 

If it contains anything but 0123456789abcdefghijklmnopqrstuvwxyz then I need to mark it as invalid.

 

if ($keyword contains ABCDEFGHIJKLMNOPQRSTUVWXYZ!@#$%^&*()_+{}|":<>?/.,;'[]\=-){
   $Error_msg = "invalid keyword";
}

 

I don't really know much about preg_replace or similar functions...but I presume I would need to use something like that. 

 

I appreciate any guidance/examples.

[Pikachu2000]

This ought to point you down the right path.

$string = 'abcdefghi12345A';
if(preg_match('~[^a-z0-9]~', $string) ) {
echo 'Bad chars';
}