I am a noob at web dev but have been trying to improve my skills over the last few months. I have made this sign up script for my website that runs when a user has filled in their details and clicks sign up. The purpose is to pass their details into my SQL database. It isn't working though and just shows a blank white page with no error messages.
The code below is my file called signup.inc.php
<?php
if (isset($_POST["submit"])) {
    
    $name = $_POST["name"];
    $email = $_POST["email"];
    $username = $_POST["uid"];
    $pwd = $_POST["pwd"];
    $pwdRepeat = $_POST["pwdrepeat"];
    // require_once 'dbh.inc.php';
    require_once 'functions.inc.php';
    if(emptyInputSignup($name, $email, $username, $pwd, $pwdRepeat) !== false) {
        header("location: ../signup.php?error=emptyinput");
        exit();
    }
    if(invalidUid($username) !== false) {
        header("location: ../signup.php?error=invaliduid");
        exit();
    }
    if(invalidEmail($email) !== false) {
        header("location: ../signup.php?error=invalidemail");
        exit();
    }
    if(pwdMatch($pwd, $pwdRepeat) !== false) {
        header("location: ../signup.php?error=passwordsdontmatch");
        exit();
    }
    if(uidExists($conn, $username, $email) !== false) {
        header("location: ../signup.php?error=usernametaken");
        exit();
    }
    // createUser($conn, $name, $email, $username, $pwd);
}
else {
    header("location: ../signup.php");
    exit();
}
It calls dbh.inc.php which I use whenever I want to connect to my main database. dbh.inc.php is below.
$servername = "localhost";
$username = "asad";
$password = "";
$dbname = "tpsc";
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
} 
I want this to work whereby a user can fill in their details on the sign up page and the variables are then passed to these scripts to be put into my database. I have attached the relevant section of the sign up page below for reference:
<section class="signup-form">
        <h2>Sign Up</h2>
        <form action="includes/signup.inc.php" method="post">
            <input type="text" name="name" placeholder="Full Name">
            <input type="text" name="email" placeholder="Email Address">
            <input type="text" name="uid" placeholder="Username">
            <input type="password" name="pwd" placeholder="Password">
            <input type="password" name="pwdrepeat" placeholder="Confirm Password">
            <button type="submit" name="submit">Sign Up!</button>
        </form>
    <?php
        if (isset($_GET["error"])) {
            if ($_GET["error"] == "emptyinput") {
                echo "<p class='psyel'>Fill in all fields!</p>";
            }
            else if ($_GET["error"] == "invaliduid") {
                echo "<p class='psyel'>Choose a propper username!</p>";
            }
            else if ($_GET["error"] == "invalidemail") {
                echo "<p class='psyel'>Choose a propper email!</p>";
            }
            else if ($_GET["error"] == "passwordsdontmatch") {
                echo "<p class='psyel'>Passwords do not match!</p>";
            }
        }
    ?>
Apologies in advance if their are obvious mistakes or if the solution is quite simple. I am still in the learning stages.
 
    