PHP: Simple, Validate if string is hex?

Question

I have no clue how to validate this string. I am simply supplying an IV for an encryption, but can find no 1is_hex()1 or similar function, I can’t wrap my head around it! I read on a comment in the php documentation (user contrib. notes) this:

if($iv == dechex(hexdec($iv))) {   //True } else {   //False } 

But that doesn't seem to work at all.. It only says false. If it helps my input of my IV would be this:

92bff433cc639a6d 

Answer 1

Use function : ctype_xdigit

<?php $strings = array('AB10BC99', 'AR1012', 'ab12bc99'); foreach ($strings as $testcase) {     if (ctype_xdigit($testcase)) {         echo "The string $testcase consists of all hexadecimal digits.\n";     } else {         echo "The string $testcase does not consist of all hexadecimal digits.\n";     } } ?>  

The above example will output:

• The string AB10BC99 consists of all hexadecimal digits.
• The string AR1012 does not consist of all hexadecimal digits.
• The string ab12bc99 consists of all hexadecimal digits.

Answer 2

Another way without ctype or regex:

$str = 'string to check';  if (trim($str, '0..9A..Fa..f') == '') {     // string is hexadecimal }