PHP 函数 ctype_xdigit()

<?php
   $strings = array('ABCDEF', 'SAI!@#$', 'ab12bc99');

   foreach ($strings as $test) {
      if (ctype_xdigit($test)) {
         echo "$test consists of all hexadecimal digits. \n";
      }else {
         echo "$test does not have all hexadecimal digits. \n";
      }
   }
?>