SQL error that i could not figure it out - php

Question

This is the code:
<?php
try
{
$bdd = new PDO('mysql:host=localhost;dbname=mydatabase;charset=utf8', 'root', '',array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
}
catch(Exception $e)
{
die('Erreur : '.$e->getMessage());
}
$req = $bdd->prepare('SELECT nom FROM jeux_video WHERE possesseur = ?');
$req->execute(array($_GET['possesseur']));
while($data = $req->fetch()){
echo $data['nom'].'<br/>';
}
$req->closeCursor();
?>
and this is the error:
Notice: Undefined index: possesseur in /opt/lampp/htdocs/openclassroom/index.php on line 12

Answer 1

The variable "possesseur" is not passed in the URL like that
script.php?possesseur=TEST
It is not a Mysql error, it is a PHP notice

Answer 2

$req->execute(array($_GET['possesseur']));
You're not checking if $_GET['possesseur'] exists. Add an if clause in it:
<?php
try
{
$bdd = new PDO('mysql:host=localhost;dbname=mydatabase;charset=utf8', 'root', '',array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
}
catch(Exception $e)
{
die('Erreur : '.$e->getMessage());
}
if (isset($_GET['possesseur'])) {
$req = $bdd->prepare('SELECT nom FROM jeux_video WHERE possesseur = ?');
$req->execute(array($_GET['possesseur']));
while($data = $req->fetch()){
echo $data['nom'].'<br/>';
}
$req->closeCursor();
}