user_delete.php

<?php

session_start();
require "core/config.php";

if (!isset($_GET["username"])) {
    header("location: index.php");
    exit();
}

try {
    $user = $connection->query("SELECT username FROM user WHERE username = '{$_GET['username']}'");
    if ($user->num_rows < 1) {
        header("location: index.php");
        exit();
    }

    $connection->query("DELETE FROM user WHERE username = '{$_GET['username']}'");
    $connection->query("DELETE FROM post WHERE author = '{$_GET['username']}'");
    $connection->query("DELETE FROM relation WHERE from_user = '{$_GET['username']}'");
    $connection->query("DELETE FROM relation WHERE to_user = '{$_GET['username']}'");

    $_SESSION["message"] = "User was deleted successfully";
    $_SESSION["message-type"] = "primary";

    header("location: index.php");
    exit();
} catch (Exception $e) {
    $_SESSION["message"] = "Something went wrong";
    $_SESSION["message-type"] = "danger";

    header("location: index.php");
    exit();
}
?>