allow certain characters

[aebstract]

How can I check a string to see if it only contains certain characters, and if it contains anything else then it will let me know.

 

Say I have $string and I wanna make sure it only contains a,b,c,d,e,f,0,1,2,3,4,5,6,7,8, or 9 and if it contains anything else then it will return an error?

[discomatt]

Several ways... Regex:

 

<?php
$safelist = 'abcdef0123456789'; // any metacharacters in here (-, [, ], ect) must be escaped with \
$regex = '/[^'.$safelist.']/i';

if (preg_match($regex, $subject) )
   return FALSE; // found a bad character
?>

 

You could also explode your subject into an array of characters and use in_array, but I think this would be much slower.

 

You could also use strpos, and use an array of the disallowed character as $needle... but once again, I think this would be slower

[discomatt]

As a second note, in the regex example, you can even use ranges to make things easier

 

$safelist='a-f0-9';

 

or

 

$safelist='a-f\d';