PHP generate random string function_PHP tutorial

/**
* Generate a random string
*
* Generate a random string of specified length and return it to the user
*
* @access public
* @param int $len Generate Number of digits in string
* @return string
*/  
function randStr($len=6) {  
$chars='ABDEFGHJKLMNPQRSTVWXYabdefghijkmnpqrstvwxy23456789#%*'; // characters to build the password from  
mt_srand((double)microtime()*1000000*getmypid()); // seed the random number generater (must be done)  
$password='';  
while(strlen($password)<$len)  
$password.=substr($chars,(mt_rand()%strlen($chars)),1);  
return $password;  
} 

?>