php生成随机数 自定义函数 randstr($length)

function randstr($len=6){

$chars='abcdefghijklmnopqrstuvwxyz0123456789';

#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;

}

$salt = randstr();