Notice: Undefined variable but I already defined it - php

Question

I'm having a problem and I can't find a solution. I'm getting this error "Notice: Undefined variable: id_horaire". But I defined it and I don't know how to fix that.
Here's my code :
<?php
require_once '../database.php';
if (!$_SESSION['admin']) {
header('location:login.php');
exit();
}
if(isset($_GET['id']) AND !empty($_GET['id'])) {
$id_horaireSecure = htmlspecialchars($_GET['id']);
$id_horaire = $db->prepare('SELECT * FROM runaway.horaire WHERE id = ?');
$id_horaire->execute(array($id_horaireSecure));
}
if(!empty($_POST['heure_ouverture']) AND !empty($_POST['heure_fermeture'])) {
$heure_ouverture = ($_POST['heure_ouverture']);
$heure_fermeture = ($_POST['heure_fermeture']);
$update = $db->prepare('UPDATE runaway.horaire SET heureOuverture=?, heureFermeture=?');
$update->execute(array($heure_ouverture, $heure_fermeture));
$message = "L'horaire a bien été mise à jour";
header('location:login.php');
exit();
} else {
$message = 'Les champs ne sont pas tous remplis';
}
?>
<div class="phpContainer">
<h2>Changer les horaires d'ouverture du Lundi</h2>
<div class="form col-12">
<div class="contact-form container">
<form method="post" enctype="multipart/form-data">
<div class="input-container">
<input type="text" name="heure_ouverture" class="input" value="<?=$id_horaire['heureOuverture'] ?>" />
<label for="">Heure d'ouverture</label>
<span>Heure d'ouverture</span>
</div>
<div class="input-container">
<input type="text" name="heure_fermeture" class="input" value="<?=$id_horaire['heureFermeture'] ?>" />
<label for="">Heure de fermeture</label>
<span>Heure de fermeture</span>
</div>
<input type="submit" value="Modifier l'horaire" class="boutonForm">
</form>
</div>
</div>
<br>
<?php if(isset($message)) {
echo $message;
}
?>
</div>
Thank you !
ps: I'm french, which is why some variables and text may seem strange to you

Answer 1

The problem is you declare $id_horaire only if this condition isset($_GET['id']) AND !empty($_GET['id']) met.
You can either give it a default value before the if, or you need to change your logic.