Trying to check if username already exists in MySQL database using PHP

Question

I\'ve looked at the many other posts that were similar to my issue and implemented their solutions (as far as I can tell) as exactly as I could. However, every time I execut

Answer 1

$firstname = $_POST["firstname"];
$lastname = $_POST["lastname"];
$email = $_POST["email"];
$pass = $_POST["password"];

$check_email = mysqli_query($conn, "SELECT Email FROM crud where Email = '$email' ");
if(mysqli_num_rows($check_email) > 0){
    echo('Email Already exists');
}
else{
    if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $result = mysqli_query($conn, "INSERT INTO crud (Firstname, Lastname, Email, Password) VALUES ('$firstname', '$lastname', '$email', '$pass')");
}
    echo('Record Entered Successfully');
}

Answer 2

$query = mysql_query("SELECT username FROM Users WHERE username='$username' ")

Use prepared statements, do not use mysql as it is deprecated.

// check if name is taken already
$stmt = $link->prepare("SELECT username FROM users WHERE username = :username");
$stmt->execute([
    'username' => $username
]);
$user = $stmt->fetch(PDO::FETCH_ASSOC);

if (isset($user) && !empty($user)){
    // Username already taken
}