Delete multiple mysql rows with check box not working - php

Question

Here Is my problem: I do not get any error with my code but my problem is when i click the 'Delete Multiple' Button it does nothing not even reload the page.
Note: By The Way the redirect_to(); function i created so do not get confused by thinking that is a php function or anything
PHP Code:
display_errors(E_ALL);
if(isset($_POST['muldelete'])) {
$mul = $_POST['checkdelete'];
$sql = "DELETE FROM cmarkers WHERE id = " . $mul;
$result = mysqli_query($db, $sql);
redirect_to("elerts.php");
}
HTML Code:
<form action="elerts.php" method="post">
<table class="table table-striped">
<tr>
<td> </td>
<td>Date</td>
<td>Comment</td>
<td>Actions</td>
</tr>
<?php
$sql = "SELECT * FROM cmarkers";
$result = $db->query($sql);
while ($row = mysqli_fetch_assoc($result)) {
?>
<tr>
<td><input type="checkbox" name="checkdelete[]" value="<?php echo $row['id']; ?>" /></td>
<td><?php echo $row['date']; ?></td>
<td><?php echo $row['comment']; ?></td>
<td>DeleteEdit</td>
</tr>
<?php
}
?>
<input type="submit" name="muldelete" value="Delete Multiple" />
</table>
</form>
Thank You
If you need more info please let me know

Answer 1

First, your code contain some attention and placements errors.
input between <table> outer of td's is incorrect.
You can't make a multiple delete if you generate one form by value to
delete.
Fix them.
Getting Array of muldelete
To all the checked inputs, you must add the array field symbol
to clusterize the name "muldelete" to a post array.
<td><input type="checkbox" name="checkdelete[]" value="<?php $row['id']; ?>" /></td>
PHP side
Now you can fetch whole deletion array, like this:
if(!empty($_POST["muldelete"]))
{
$mul = join(',', $_POST['checkdelete']);
// Using IN() to make only one query for all records instead of multiple
// ex: IN(3, 4, 54, 8)
$query = "DELETE FROM cmarkers WHERE id IN(".$mul.")";
$result = mysqli_query($db, $query);
redirect_to("elerts.php");
}
Security
If ID's are integer value, you can prevent string injection into the sql query
$mul = array_map(function($id)
{
return intval($id);
}, $mul);

Answer 2

Your button is outside the <form></form> tags, so it is not related to the form elements or the form method at all. Instead of having a different form for each checkbox you should surround the entire table with the form tags thus ensuring that all the checkboxes and the button are in the same form.
<form method='post' action='elerts.php'>
<table class="table table-striped">
...all your table data including checkboxes...
<input type="submit" name="muldelete" value="Delete Multiple" />
</table>
</form>

Answer 3

I think because You are closing form tag earlier than submit button.
Try to put whole table into and should work.
PHP should looks like
display_errors(E_ALL);
if(isset($_POST['muldelete'])) {
$mul = implode(',',$_POST['checkdelete']);
$sql = "DELETE FROM cmarkers WHERE id IN(" . $mul.")";
$result = mysqli_query($db, $sql);
redirect_to("elerts.php");
}