PHP | 404 Object not Found - php

Question

i have a problem with my website. it should get a Login/Sign Up website. If i type in my First and Last name, password and so, i click on submit and 404 Object not Found Appears. The Files are in the correct directory... btw, im not using a htaccess file yet so u dont need to ask for it.
sry for my basic english :)
`
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, $_POST['pwd']);
//error handler
//Check for empty fields
if (empty($first) || empty($last) || empty($email) || empty($uid) || empty($pwd)) {
header("Location: ../signup.php?signup=empty")
exit();
} else {
//Check if inputs are valid
if (!preg_match("/^[a-zA-Z]*$/", $first) || !preg_match("/^[a-zA-Z]*$/", $first) ) {
header("Location: ../signup.php?signup=invalid")
exit();
} else {
//check if email is valid
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
header("Location: ../signup.php?signup=email")
exit();
} else {
$sql = "SELECT * FROM users WHERE user_id='$uid'";
$result = mysqli_query($conn, $sql);
$resultCheck = mysqli_num_rows($results);
if ($resultCheck > 0) {
header("Location: ../signup.php?signup=usernametaken")
exit();
} else {
//hashing passwords
$hashedPwd = password_hash($pwd, PASSWORD_DEFAULT);
//Insert the user into DB
$sql = "INSER INTO users (user_first, user_last, user_email, user_uid, user_pwd) VALUES ('$first', '$
last', '$email', '$uid', '$hashedPwd');";
$result = mysqli_query($conn, $sql);
header("Location: ../signup.php?signup=succes")
exit();
}
}
}
} else {
header("Location: ../signup.php")
exit();
}`

Answer 1

As far as I know you can't use '..' notation in header('location:'). Browsers don't understand '..' notation.
You should use either a fully qualified URL or a relative URL:
header('Location: http://example.com/your-subdirectories/signup.php') ;
header('Location: /your-subdirectories/signup.php') ;
This question has already been answered on Stack Overflow