Mysqli query doesn't execute
<p>I'm here with a "strange" problem. </p>

<p>This is how i create a new topic. 
If sesson isnt set go back to index.php, or if is set it connects to db, get informations from form and put them into db. Then if is all ok browser go back to index.php. This works fine:</p>

<pre><code>&lt;?php 
    session_start();

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

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

        include ('../modules/dbconnect.php');

        $uname = $_SESSION['username'];
        $utitle = $_POST["title"];
        $utext = $_POST["myTextArea"];

        $query = mysqli_query($conn, "INSERT INTO topic (author, title, text) VALUES ('$uname', '$utitle','$utext')");

        if($query){header("Location: ../index.php");}

        $conn-&gt;close();
    }
?&gt;

&lt;form class="registration_form" action="" method="post"&gt;
    &lt;label&gt;Titolo&lt;/label&gt;
    &lt;input type="text" name="title" class="input"&gt;
    &lt;label&gt;Testo&lt;/label&gt;
    &lt;textarea name="myTextArea"&gt;&lt;/textarea&gt;
    &lt;input class="button" type="submit" name="submit" value="submit"&gt;
&lt;/form&gt;
</code></pre>

<p>And this is my problem. I've used the same structure to insert post after i enter into a topic but i don't know why this doesnt work and i can't figure out what's the problem:</p>

<pre><code> &lt;?php
      if(isset($_POST["submit"])){

         include('modules/dbconnect.php');

         $id = $_GET['id'];
         $uname = $_SESSION['username'];
         $utext = $_POST["myText"];

         $query = mysqli_query($conn, "INSERT INTO post (id, author, text) VALUES ('$id, '$uname', '$utext')");

         if($query){header("Location: ../index.php");}

         $conn-&gt;close();
     }
 ?&gt;

 &lt;form class="reply_form" action="" method="post"&gt;
     &lt;label&gt;Testo&lt;/label&gt;
     &lt;textarea name="myText"&gt;&lt;/textarea&gt;
     &lt;input class="button" type="submit" name="submit" value="submit"&gt;
 &lt;/form&gt;
</code></pre>