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.