Generate v4 UUID

gistfile1.php

<?php

function uuidgen() { // generate a version 4 UUID
  // clarification: a v4 UUID is in the form xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
  // where any x is a random alphanumeric character
  // 4 is the numeral 4
  // and y may only by one of 8, 9, A or B
  
  $format = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx';
  $x = '1234567890ABCDEF';
  $y = '89AB';
  
  $uuid = '';
  
  $format = str_split($format);
  foreach ($format as $char) {
    if ($char == 'x' || $char == 'y') {
      mt_srand(make_seed()); // seed the random generator
      $uuid .= ${$char}[mt_rand(0, strlen(${$char})-1)];
    } else {
      $uuid .= $char;
    }
  }
  
  return $uuid;
}

function make_seed() { // http://cl.ly/3L23
  list($usec, $sec) = explode(' ', microtime());
  return (float) $sec + ((float) $usec * 100000);
}

?>