Récupérer depuis GET

<?php
session_start();
include("config.php");
if(isset($_SESSION['id_session']))
 {$id=$_SESSION['id_session'];
if($_GET["Id_pub"] === "") echo "a is an empty string\n";
if($_GET["Id_pub"] === false) echo "a is false\n";
 }
  ?>

if(isset($_SESSION['id_session']))
 {
 $id=$_SESSION['id_session'];
 include("config.php");
  $res=mysqli_query($base,"select * from utilisateur where Id_p='$id'"); 
  $l=mysqli_fetch_array($res);
 $res=mysqli_query($base,"select * from publication where Id_p='$id'");
 while($l=mysqli_fetch_array($res))
  { 
 echo'<div class="block_pub">';
 echo'<div class="block_p">';
  echo'<img src="'.$l[6].'">';
  echo'<br><br>';

  echo"<div><a href='detailpublicationn.php?Id_pub=$l[1]' rel="nofollow noopener noreferrer" target="_blank"><h5>$l[2] à $l[4]</h5></a></div><br>'";
  echo'</div>';echo'</div>';echo'</div>';

EDIT : Ajout des balises de code