Finn fem fel

<?php

if(isset($_POST["register"])) {

    $username = $_POST["username"];
    $password = $_POST["password"];
    $database = "Database.txt";

    $userdata = $username . " : " . password_hash($password, PASSWORD_DEFAULT) . PHP_EOL;

    $databaseString = file_get_contents($database);
    $databaseUserRow = explode("\n", $databaseString);

    foreach($databaseUserRow as $user) {

        $user = explode(" : ", $user);
        echo $user[0] . "<br />";

        if($username === $user[0]) {
            echo "Username already exists.";
        }

        else {
            file_put_contents($database, $userdata, FILE_APPEND);
        }
    }

}

?>