将内容从 PHP 文件添加到数据库时出现问题

所以事情是这样的，我不确定我的数据库是否连接成功，如果是，那么我的输入查询不起作用。这是我所拥有的。我相信我的错误相当明显，我可能会踢自己，但请帮助。

.HTML：

<form action="adduser.php" method="post">
    <label>Create Username</label><br>
    <input type="text" name="username" placeholder="Username" /><br>
    <label>Create Password</label><br>
    <input type="password" name="password" placeholder="Password" /><br>
    <label>Confirm Password</label><br>
    <input type="password" placeholder="Password" /><br>
    <label>Select Gender</label><br>
    <input type="radio" name="gender" value="Male">Male</button>
    <input type="radio" name="gender" value="Female">Female</button><br>
    <label>Click submit to continue</label><br>
    <button class="btn btn-primary" name="submit" type="submit">Submit</button>
   </form>

连接.php：

<?php
$username = "********";
$password = "***********";
$db = "localhost";
$dbconn = mysql_connect($db, $username, $password);
    if (!$dbconn){
        die ("Connection failure!");
    }
    return "Connection Successful.";
    mysql_select_db("who_do_it_db", $dbconn);
?>

添加用户.php：

<?php
include 'connect.php';
$uName = $_POST['username'];
$pWord = $_POST['password'];
$gender = $_POST['gender'];
$query = 'INSERT INTO users(Username, Password, Gender) VALUES ("$uName","$pWord","$gender");';
$query = mysql_query($query);