Connecting mySQL db through PHP

Question

Let me begin by saying I am extremely new at this. I am trying to develop a mobile app and a website with no real experience. There is likely something that I have missed or I am doing wrong but I cannot seem to pin point where the issue is. Prior to creating my own, I followed a video guide (with the demo files downloaded to my computer) but cannot seem to connect to my database. I have also copied the demo files and placed them into my code and it is still getting me caught on one section. I am using the program MAMP for the connection and Brackets for the code. Below are my session files:

Database connection-

<?php

$dbServername = "localhost";
$dbUsername = "root";
$dbPassword = "root";
$dbName = "Login System";

$con = mysqli_connect($dbServername, $dbUsername, $dbPassword, $dbName);

My sign up document-

<?php

if (isset($_POST['submit'])) {

    include_once 'dbh.inc.php';

    $first = mysqli_real_escape_string($conn, $_POST['first']);
    $last = mysqli_real_escape_string($conn, $_POST['last']);
    $email = mysqli_real_escape_string($conn, $_POST['email']);
    $uid = mysqli_real_escape_string($conn, $_POST['uid']);
    $pwd = mysqli_real_escape_string($conn, $_POST['pwd']);

    //Error handlers
    //Check for empty fields
    if (empty($first) || empty($last) || empty($email) || empty($uid) || empty($pwd)) {
        echo <h2>Please fill in all fields;
        exit ();
    } else {
        //Check if input characters are valid
        if (!preg_match("/^[a-zA-Z]*$/", $first) || !preg_match("/^[a-zA-Z]*$/", $last)) {
            header("Location: ../signup.php?signup=invalid");
            exit();
        } else {
            //Check if email is valid
            if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
                header("Location: ../signup.php?signup=email");
                exit();
            } else {
                $sql = "SELECT * FROM users WHERE user_uid='$uid'";
                $result = mysqli_query($conn, $sql);
                $resultCheck = mysqli_num_rows($result);

                if ($resultCheck > 0) {
                    header("Location: ../signup.php?signup=usertaken");
                    exit();
                } else {
                    //Hashing the password
                    $hashedPwd = password_hash($pwd, PASSWORD_DEFAULT);
                    //Insert the user into the database
                    $sql = "INSERT INTO users (first, last, email, uid, pwd) VALUES ('$first', '$last', '$email', '$uid', '$hashedPwd');";
                    mysqli_query($conn, $sql);
                    header("Location: ../signup.php?signup=success");
                    exit();
                }
            }
        }
    }

} else {
    header("Location: ../signup.php");
    exit();
}

?>

My Login Sheet

    <?php
    include_once 'header.php';
?>

    <section class="main-container">
        <div class="main-wrapper">
            <h2>Signup</h2>
            <form class="signup-form" action="includes/signup.inc.php" method="POST">
                <input type="text" name="first" placeholder="Firstname">
                <input type="text" name="last" placeholder="Lastname">
                <input type="text" name="email" placeholder="E-mail">
                <input type="text" name="uid" placeholder="Username">
                <input type="password" name="pwd" placeholder="Password">
                <Button type="submit" name="submit">Sign up</Button>
            </form>

        </div>
    </section>

<?php
    include_once 'footer.php';
?>

I have reset the password for 'root' to 'root' and ensured I can login with that. The document that checks for error's lists if any field is empty, return to the previous page with the word "=empty" in the url. No matter what I type into my fields, it is either not pushing the information into the database or I have incorrectly mapped my fields so one of the database fields is empty.

Any help would be greatly appreciated. As I said at the beginning of this post, I am extremely new at this. You may see something that is incredibly obvious and somewhat dumb... you've been warned! I am working on creating a mobile application and website that allows users to login. The login attempt will reference my localhost database to confirm that the user does not exist or that the user is not in use.

Thank you!

Answer 1

To check the connection handling, you can add this after the connect attempt:

$conn = mysqli_connect( ... );

if ( !$conn ) {
    die( 'Did not connect: ' . mysqli_connect_error() ); 
}

To check the handling after a query, you can add this after the query attempt:

$result = mysqli_query( $conn, $sql );

if (false === $result) {
    die( 'Query error: ' . mysqli_error($conn) );
}