Generate somewhat strong unique identifiers

UIDGenerator.php

<?php

/**
 * Generate somewhat strong unique identifiers
 * Example usage:
 * - create non standard mysql ids
 * - create app key/secret for OAuth
 * - ...
 *
 * @return string containing the unique identifier
 */
function generateUid() {
  $fp = fopen('/dev/urandom','rb');
  $entropy = fread($fp, 32);
  fclose($fp);
  // in case /dev/urandom is reusing entropy from its pool, let's add a bit more entropy
  $entropy .= uniqid(mt_rand(), true);
  $hash = sha1($entropy);
  // if you're obsessed w/ security use the following instead
  // $hash = hash('sha256', $entropy)
  return $hash;
}