What's wrong with my code?

Question

This is the code:

<?php
session_start();
$db = mysqli_connect("localhost", "root", "", "authentication");
if (isset($_POST['register_btn'])) {
session_start();

$username=mysql_real_escape_string($_POST['username']);
$email=mysql_real_escape_string($_POST['email']);
$password=mysql_real_escape_string($_POST['password']);
$password2=mysql_real_escape_string($_POST['password2']);
if ($password==$password2) {
$password=md5($password);
$sql="INSERT INTO users(username, email, password) VALUES('$username', '$email', '$password')";
msqli_query($db, $sql);
$_SESSION['message'] = "You are now logged in";
$_SESSION['username'] = $username;
header("location:game.html");
}
else{
$_SESSION['message'] = "The two passwords do not match";
}
}
?>

When I open in localhost show me this error:

Fatal error: Uncaught Error: Call to undefined function mysql_real_escape_string() in C:\Users\Paul\Downloads\desktop\paul\htdocs\registration form\register.php:5 Stack trace: #0 {main} thrown in C:\Users\Paul\Downloads\desktop\paul\htdocs\registration form\register.php on line 5

Answer 1

Try mysqli_real_escape_string() instead, I noticed you use mysqli.

Answer 2

I think you should link your code for better response

Answer 3

What did you say didn t functioned the problem in the same whan I finish to complete the email password and username and when I press the button register it shows me that error

Answer 4

Okay

Answer 5

In the header file is a game but maybe this is the problem

Answer 6

Is not a problem with the game fron header file is a problem with this code buy i don t know what s wrong
this is the sintax:
$username=mysql_real_escape_string($_POST['username']);

Answer 7

thanks for everyone I obtained a good code at least