带有复选框的表单中的奇怪重定向

The problem is that in chrome when i click on submit the php file is not called and redirect me to enother html page, in firefox when I select three checkboxes it redirect to that html page the same on chrome. I tried to use radio instead of checkbox but it has the same problem. If i use imput text instead checkbox it works!! Can sameone help meee?!?!?

this is the form:

<form action="editOpenedDays.php" method="post">
  <input type="checkbox" name="lunedi" value="lun"/>Lunedì<br>
  <input type="checkbox" name="martedi" value="mar"/>Martedì<br>
  <input type="checkbox" name="mercoledi" value="mer"/>Mercoledì<br>
  <input type="checkbox" name="giovedi" value="gio"/>Giovedì<br>
  <input type="checkbox" name="venerdi" value="ven"/>Venerdì<br>
  <input type="checkbox" name="sabato" value="sab"/>Sabato<br>
  <input type="checkbox" name="domenica" value="dom"/>Domenica<br><br>
  <input type="submit" name="submit" value="Inserisci/Modifica">
</form>

<?php
include 'connect.php';

$ID = $_SESSION['userId'];

$days['lunedi'] = isset($_POST["lunedi"]) ? $_POST["lunedi"] : "";
$days['martedi'] = isset($_POST["martedi"]) ? $_POST["martedi"] : "";
$days['mercoledi'] = isset($_POST["mercoledi"]) ? $_POST["mercoledi"] : "";
$days['giovedi'] = $isset($_POST["giovedi"]) ? $_POST["giovedi"] : "";
$days['venerdi'] = isset($_POST["venerdi"]) ? $_POST["venerdi"] : "";
$days['sabato'] = isset($_POST["sabato"]) ? $_POST["sabato"] : "";
$days['domenica'] = isset($_POST["domenica"]) ? $_POST["domenica"] : "";

$formattedDays = null;

foreach ($days as $day){

}

if ($days != null){
    $stmt=$conn->prepare();
    $stmt->bind_param("s", $formattedDays);
    $stmt->execute();
    header("Location: informazioni.php");
}
else{
    echo "Non sono state inseriti giorni di apertura";
}

PS: sorry for my english

</div>

$isset($_POST["giovedi"])

Try to remove the '$' on isset(). ;)

And BTW, you can replace this :

$days['lunedi'] = isset($_POST["lunedi"]) ? $_POST["lunedi"] : "";
$days['martedi'] = isset($_POST["martedi"]) ? $_POST["martedi"] : "";
$days['mercoledi'] = isset($_POST["mercoledi"]) ? $_POST["mercoledi"] : "";
$days['giovedi'] = isset($_POST["giovedi"]) ? $_POST["giovedi"] : "";
$days['venerdi'] = isset($_POST["venerdi"]) ? $_POST["venerdi"] : "";
$days['sabato'] = isset($_POST["sabato"]) ? $_POST["sabato"] : "";
$days['domenica'] = isset($_POST["domenica"]) ? $_POST["domenica"] : "";

By this :

$dayTab = array('lunedi', 'martedi', 'mercoledi', 'giovedi', 'venerdi', 'sabato', 'domenica');
foreach($dayTab as $day) {
    $days[$day] = $_POST[$day] ?: '';
}