自已隨手寫的一個 Function    function getRandomKey($_len) {        srand((double)microtime()*1000000);        $chars = "abcdefghijkmnopqrstuvwxyz023456789";        $i = 0;        $key = '' ;        for($i=0;$i<$_len;$i  ) {            $num = rand() % 33;            $tmp = substr($chars, $num, 1) ;            $key .= $tmp ;        }        return $key ;    }