example

<?php

function unique_id($length) {
  $rnd1 = mt_rand(0,10000);
  $rnd2 = mt_rand(0,10000);
  $rnd3 = mt_rand(0,10000);

  $hash = str_shuffle(sha1($rnd1).md5(microtime()).sha1($rnd2.microtime()).md5($rnd3));
  return substr($hash, 0, $length);
}

/**
 * whoi, lets give feedback and
 * show us some random-ids with
 * a seckey / imploded with ; /
 */
$qnt = 40;
for($i = 0; $i < $qnt; $i++) {
  echo implode(';',array(
    unique_id(20),
    unique_id(8),
  ));
  echo '<br />';
}

/** reult:
 * 2ccf5e17999e0550c263;79ea79d7
 * 9a50a23399b0a8e19d5e;099fb725
 * f90a2d5b75f8.1deb8fd;3773061c
 * 8ee9c480f5006334.cb5;e4f8048e
 * 4f1f12a29b5c592e0a9b;4 f20d7a
 * 4019620d0853cff290.7;058823d4
 * abdb1681718bcd6859e1;5066.040
 * 412df0f70f51b98efdc9;f583c0f7
 * 692e85693fab3345a1e0;c0e22c1e
 * e450f8879563d30aa472;42dc1197
 * ..and so on..
 * 1st row:
 * unique-id:   2ccf5e17999e0550c263
 * secKey:  79ea79d7
**/

?>