php写注册接口给第三方调用

if($_POST){    if ($id == '') {        $res = urlencode("Please enter username");        exit(json_encode($res));     }        $rt_user = $db->get_one("SELECT member_id FROM `{$tablepre}member_table` WHERE member_id = '{$id}' LIMIT 1");    $count = mysql_num_rows($rt_user);     if ($count > 0) {        exit(json_encode(1));     } else {        $row = array(            'member_class' => 1,            'member_id' => $id,            'member_pass' => $password,            'member_tel1'=>$member_tel11,            'base_pass' => $base_pass,            'register_date' => $m_now_time        );                $insert_id = $db->insert("{$tablepre}member_table",$row);        exit(json_encode(0));     }}

写了一个注册接口， 和写注册是差不多，就是返回值用json_encode，返回不同的值来表示注册出错的原因