[PHP] Compare versions with alphabetical components

safe_version_compare.php

<?php
/**
 * Compare versions with alphabetical components.
 * Usesversion_compare after having converted single chars to their decimal values.
 * Needed because version_compare does not understand versions like '2.5.c'.
 *
 * @param string $a
 * @param string $b
 * @param string $op
 */
function safe_version_compare($a, $b, $op=null)
{
  $replace_chars = create_function('$m', 'return ord(strtolower($m[1]));');
  
  // add dot before groups of letters (version_compare does the same thing)
  $a = preg_replace('#([0-9]+)([a-z]+)#i', '$1.$2', $a);
  $b = preg_replace('#([0-9]+)([a-z]+)#i', '$1.$2', $b);
  
  // apply ord() to any single letter
  $a = preg_replace_callback('#\b([a-z]{1})\b#i', $replace_chars, $a);
  $b = preg_replace_callback('#\b([a-z]{1})\b#i', $replace_chars, $b);
  
  if (empty($op))
  {
    return version_compare($a, $b);
  }
  else
  {
    return version_compare($a, $b, $op);
  }
}