hex to string in PHP

hex_to_string.php

<?php
  function hex_to_string ($hex) {
    if (strlen($hex) % 2 != 0) {
      throw new Exception('String length must be an even number.', 1);
    }
    $string = '';
  
    for ($i = 0; $i < strlen($hex) - 1; $i += 2) {
      $string .= chr(hexdec($hex[$i].$hex[$i+1]));
    }
    
    return $string;
  }
?>