如果它们在php中是动态的，如何存储多个复选框

hi i am trying to store multiple selected values in a new table with last inserted id.

my error is array is coming but id_facility value is not coming

here is my form:

<ul id="hostel_facility" class="dropdown-menu dropdown-select">
    <?php  $facility = $conn->query("SELECT * FROM os_facilities  ORDER BY id_facility ASC");
        while ($facilityresult = $facility->fetch_assoc()) { ?>
        <li><a><input type="checkbox" name="hostel_facility[]" value="<?php  echo$facilityresult['id_facility']; ?>" /><?php echo $facilityresult['facility_name']; ?></a></li>
    <?php } ?>
</ul>

i want to store in new table columns are id_hostel,id_facility

My form:

<ul id="hostel_facility" class="dropdown-menu dropdown-select">
    <?php  $facility = $conn->query("SELECT * FROM os_facilities  ORDER BY id_facility ASC");
        while ($facilityresult = $facility->fetch_assoc()) { ?>
        <li><a><input type="checkbox" name="hostel_facility[]" value="<?php  echo $facilityresult['id_facility']; ?>" /><?php echo $facilityresult['facility_name']; ?></a></li>
    <?php } ?>
</ul>

Here is my controller page after storing the job:

$hostelId=$conn->insert_id;
if($addHostel)
{
foreach($hostelData['hostel_facility'] as $key=>$facility)
{
    $conn->query("INSERT INTO os_hostel_facility (id_hostel,id_facility) values ('".$hostelId."','".$facility."')");
}