PHP无错误，但数据未插入数据库

我试图将表单中的数据插入mySQL数据库，没有连接错误，但没有数据插入数据库。有什么想法吗？ 这是我的HTML表单：

<div class="tab-pane" id="Registration">
                    <b><em>Listen to the voice of Soul</em></b>
                    <form class="form" role="form" method="POST" action="signup.php" accept-charset="UTF-8"id="signup-nav">
                        <div class="form-group">
                            <label class="sr-only" for="email2">Email address</label>
                            <input type="email" class="form-control"id="email2" name="signup_email" placeholder="Email address" required>
                        </div>
                        <div class="form-group">
                            <label class="sr-only" for="password2">Password</label>
                            <input type="password" class="form-control" id="pwd2" name="signup_pwd" placeholder="Password" required>
                        </div>  
                        <div class="form-group">
                            <label class="sr-only" for="password3">Confirm Password</label>
                            <input type="password" class="form-control" id="pwdcon" name="signup_pwdcon" placeholder="Confirm Password" required>
                        </div>  
                        <div class="form-group">
                            <input type="submit" name="signUpBtn" value="Sign Up" class="btn btn-primary btn-block"></button>
                        </div>
                    </form>
                </div>  

倾听灵魂的声音
电子邮件地址
密码
确认密码

我的数据库名是coldplay，表是userdata，im使用ID=root的本地主机，没有密码

PHP:

请先阅读和。如果您将脚本保持这种状态，那么它很容易受到sql注入的攻击

dbh.php文件中的打开php标记有问题。它应该是
你注意到dbh.php文件中php标记中的空格了吗？第一行应该是
请不要将普通密码保存到数据库。哦，我刚刚意识到我的错误！这太糟糕了，非常感谢@BenjaminPaap，问题解决了！！！
<?php

include ("dbh.php");

if(isset($_POST["signUpBtn"])){

$signup_email = $_POST ['signup_email'];
$signup_pwd = $_POST ['signup_pwd'];
$signup_pwdcon = $_POST ['signup_pwdcon'];

$sql_signup = "insert into userdata (email, pwd, pwdcon) 
values ('$signup_email', '$signup_pwd', '$signup_pwdcon')";

mysqli_query($conn, $sql_signup);

mysqli_close($conn);

header("Location: testing.html");


}

?>

<? php

$conn = mysqli_connect("localhost", "root", "", "coldplay");

if (!$conn){
    die("Connection failed: ".mysqli_connect_error());
}

?>

if (!mysqli_query($conn, $sql_signup)) {
    echo "Error: " . mysqli_error($conn);
}