ctype_xdigit
    (PHP 4 >= 4.0.4, PHP 5)
ctype_xdigit -- 
   Check for character(s) representing a hexadecimal digit
  
Description
bool 
ctype_xdigit ( string text )
   Checks if all of the characters in the provided string,
   text, are hexadecimal 'digits'.
  
Return Values
   Returns TRUE if every character in text is 
   a hexadecimal 'digit', that is a decimal digit or a character from 
   [A-Fa-f] , FALSE otherwise.
  
Examples
   
Example 1. A ctype_xdigit() example 
<?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";     } } ?>
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 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.  |  
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