Redirect on login

<?php

//Checking if both input fields are set
if (isset($_POST["username"],$_POST["password"])){
    //Checking if username/password matches your defined username/password
    if (trim($_POST["username"]) == "yourusername" && trim($_POST["password"]) == "yourpassword"){
        header("Location:https://google.com");//Redirect to google.com
        die;//Stop the script
    }
}

?>
<!DOCTYPE html>
<html lang="en">
    <head>
        <meta http-equiv="Content-Type" content="text/html;charset=utf-8">
        <title>Redirect on login</title>
    </head>
    <body>
        <form action="<?php echo $_SERVER["REQUEST_URI"]; ?>" method="post">
            <label>Username: <input type="text" name="username"></label><br>
            <label>Password: <input type="password" name="password"></label><br>
            <input type="submit">
        </form>
    </body>
</html>