为什么jQuery的$.get()收不到php的返回信息？

<code>    <p>姓名<input type="text" name="name"></p>
    <p>性别<input type="radio" name="sex" value="m">男<input type="radio" name="sex" value="f">女</p>
                    <div class="aritcle_card">
                        <a class="aritcle_card_img" href="/ai/798">
                            <img src="https://img.php.cn/upload/ai_manual/001/503/042/68b6d8dce6275464.png" alt="微信 WeLM">
                        </a>
                        <div class="aritcle_card_info">
                            <a href="/ai/798">微信 WeLM</a>
                            <p>WeLM不是一个直接的对话机器人，而是一个补全用户输入信息的生成模型。</p>
                            <div class="">
                                <img src="/static/images/card_xiazai.png" alt="微信 WeLM">
                                <span>33</span>
                            </div>
                        </div>
                        <a href="/ai/798" class="aritcle_card_btn">
                            <span>查看详情</span>
                            <img src="/static/images/cardxiayige-3.png" alt="微信 WeLM">
                        </a>
                    </div>
                
    <p>手机号码<input type="text" name="mobile"></p>
    <button id="sub">提交</button>
    <script type="text/javascript">
        $("#sub").click(function() {
            var name = $("input[name='name']").val();
            var sex = $("input[name='sex']:checked").attr('value');
            var mobile = $("input[name='mobile']").val();
            if (name&&sex&&mobile) {
                alert(name+sex+mobile);
                $.get('user_info_save.php',{name: name,sex: sex,mobile: mobile},function(data){console.log(data);});
            }
            else{alert("信息未填写完整");}
        });
    </script></code>

<code>$db=mysqli_connect($host,$user,$password,$database);
if($db){
        $db->query("set names utf8");//设置UTF-8编码(JSON的唯一编码)
}else{
        echo 'DATABASE_CONNECTION_DIE';//数据库连接失败
        exit;
}
$name = $_REQUEST['name'];
$sex = $_REQUEST['sex'];
$mobile = $_REQUEST['mobile'];
$sql = "insert `customer`(`name`,`sex`,`mobile`) values('".$name."','".$sex."','".$mobile."')";
$result=$db->query($sql);
echo "ok";
</code>

<code>    <p>姓名<input type="text" name="name"></p>
    <p>性别<input type="radio" name="sex" value="m">男<input type="radio" name="sex" value="f">女</p>
    <p>手机号码<input type="text" name="mobile"></p>
    <button id="sub">提交</button>
    <script type="text/javascript">
        $("#sub").click(function() {
            var name = $("input[name='name']").val();
            var sex = $("input[name='sex']:checked").attr('value');
            var mobile = $("input[name='mobile']").val();
            if (name&&sex&&mobile) {
                alert(name+sex+mobile);
                $.get('user_info_save.php',{name: name,sex: sex,mobile: mobile},function(data){console.log(data);});
            }
            else{alert("信息未填写完整");}
        });
    </script></code>

<code>$db=mysqli_connect($host,$user,$password,$database);
if($db){
        $db->query("set names utf8");//设置UTF-8编码(JSON的唯一编码)
}else{
        echo 'DATABASE_CONNECTION_DIE';//数据库连接失败
        exit;
}
$name = $_REQUEST['name'];
$sex = $_REQUEST['sex'];
$mobile = $_REQUEST['mobile'];
$sql = "insert `customer`(`name`,`sex`,`mobile`) values('".$name."','".$sex."','".$mobile."')";
$result=$db->query($sql);
echo "ok";
</code>

<code>$.get('user_info_save.php',{name: name,sex: sex,mobile: mobile},function(data){console.log(data);},'JSON')</code>