function random_password($len=15) {
  $str='zxcvbnmasdfghjkqwertyupZXCVBNMASDFGHJKQWERTYUP23456789';

  $pass='';
  if($len<8) $len=8;

  if(file_exists('/dev/random')) {
    $rand=fopen("/dev/random","r");
  } else if(file_exists('/dev/urandom')) {
    $rand=fopen("/dev/urandom","r");
  } else {
    while(strlen($pass)<$len)
      $pass.=substr($str,mt_rand(0,strlen($str)-1),1);
  }

  while(strlen($pass)<$len)
    $pass.=substr($str,intval((ord(fread($rand,1))*strlen($str))/256),1);
  return $pass;
}