Undefined index: chx

bonjours,

pouvez vous m 'expliquer pourquoi par rapport au code j'ai ce message d'erreur...merci

if (isset($_POST['correction']))
{
foreach($reponses as $cle => $reponse)
{	
$clic = $_POST[$cle];
	
if (empty($clic)&& empty($clic) !== $reponse['reponse'])
{	
$msg = '<p>veuillez remplir tous les champs</p>';
echo $msg;
}
else
if ($clic === $reponse['reponse'])
{
$point[$cle] = htmlspecialchars($clic);
echo '<p>' . $point[$cle]. '&nbsp&nbsp&nbsp&nbsp<b>' . $reponse['mot'] .'</b></p><br />';
}
else
if ($clic !== $reponse['reponse'])
{
$errors[$cle] = htmlspecialchars($clic);
echo '<p style="color:#red;"><del>' . $errors[$cle] . '&nbsp&nbsp&nbsp&nbsp<b>'.$reponse['mot'].'</del></b></p><p class="red"><b>'.$reponse['reponse'].' ' . $reponse['mot'] . '</b></p><br />';
}
}
}