php UUID一意シーケンスを生成するコード例

/**
  * Generates an UUID
  *
  * @author     Anis uddin Ahmad 
  * @param      string  an optional prefix
  * @return     string  the formatted uuid
  */
  function uuid($prefix = '')
  {
    $chars = md5(uniqid(mt_rand(), true));
    $uuid  = substr($chars,0,8) . '-';
    $uuid .= substr($chars,8,4) . '-';
    $uuid .= substr($chars,12,4) . '-';
    $uuid .= substr($chars,16,4) . '-';
    $uuid .= substr($chars,20,12);
    return $prefix . $uuid;
  }  
 
//Example of using the function -
//Using without prefix.
echo uuid(); //Returns like ‘1225c695-cfb8-4ebb-aaaa-80da344e8352′   
 
//Using with prefix
echo uuid(‘urn:uuid:’);//Returns like ‘urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344e8352′