Куча мелких фиксов, уборка мусора.

chat.php

@@ -8,11 +8,12 @@
 session_start();
 if (empty($_SESSION['uid'])) {
     header("Location: index.php");
+    exit;
 }
 require_once "config.php";
 //include_once "functions.php";
 
-$msg = filter_input(INPUT_POST, 'msg');
+$msg = $_POST['msg'] ?? null;
 $uid = $_SESSION['uid'];
 if ($msg) {
     try { db::c()->query('INSERT INTO `chat` (`user_id`, `msg`) VALUES (?i, "?s")', $uid, $msg); }