Question

I want to delete multiple users from db table with checkboxes at once. But my code doesn’t work correctly
index.php

<?php 
require 'db.php';   
$query="SELECT * FROM usr_table";
$result = $db->query($query) or die(mysqli_error($mysqli));
$num=mysqli_num_rows($result) or die(mysqli_errno());
if ($result) {
    echo '
    <form method="post" action="delete.php">
    <table id="list">   
            while ($row = $result->fetch_object()) {
        $id = $row->id;
        $fullname = $row->fullname;
        $dob = $row->dob;
        $phone= $row->phone;
        $adress= $row -> adress;
        $school = $row->school;
echo '<tr>
<td>'.$id.'</td>
<td>'.$fullname.'</td>
<td>'.$dob.'</td>
<td>'.$phone.'</td>
<td>'.$adress.'</td>
<td>'.$school.'</td>
<td><input type="checkbox" name="checkbox[]" id="checkbox[]"  method="post" value=$id />
</tr>';
    }

    // when the loop is complete, close off the list.
    echo "</table><p><input id='delete' type='submit' class='button' name='delete' value='Delete Selected Items'/></p></form>";
    }
?>

delete.php

<?php

    require 'db.php';
    $delete=$_GET['delete'];

    if($delete) // from button name="delete"
    {
        $checkbox = $_GET['checkbox']; //from name="checkbox[]"
        $countCheck = count($_GET['checkbox']);

        for($i=0;$i<$countCheck;$i++)
        {
            $del_id  = $checkbox[$i];
            $sql = "DELETE from usr_table where id = '$del_id'";
            $result = $db->query($sql) or die(mysqli_error($db));

        }
            if($result)
        {   
                header('Location: index.php');
            }
            else
            {
                echo "Error: ".mysqli_error($db);
            }
    }

?>

db.php

<?php
$db = new mysqli('localhost', 'user' ,'pass', 'table') or die(mysqli_errno());
$db->query("SET names UTF8") or die(mysqli_errno());
foreach ($_POST as $key => $value) { 
$_POST[$key] = mysqli_real_escape_string($value);
}
?>

Please help! It doesn’t work
HTML version

<form method="post" action="delete.php">
    <table id="list">   
            <thead>
                <tr>
                    <th width="5%">ID</th>

                    <th width="35%">Ad və soyad</th>
                    <th width="15%">Təvəllüd</th>
                    <th width="15%">Telefon</th>
                    <th width="20%">Ünvan</th>
                    <th width="5%">Məktəb</th>
                    <th width="5%">#</th>

                </tr>
            </thead><tr>
<td>20</td>
<td>Tural Teyyuboglu</td>
<td>1992-06-09</td>
<td>4940301</td>
<td>Baki Yasamal Zergerpalan</td>
<td>189</td>
<td><input type="checkbox" name="checkbox[]" id="checkbox[]"  method="post" value="20 "/>

</tr><tr>
<td>22</td>
<td></td>
<td>1992-06-09</td>
<td>0</td>
<td></td>
<td></td>
<td><input type="checkbox" name="checkbox[]" id="checkbox[]"  method="post" value="22 "/>
</tr><tr>
<td>23</td>
<td>Tural Turik</td>
<td>1992-06-09</td>

<td>4940301</td>
<td>Bakı Yasamal Zərgerpalan</td>
<td>189</td>
<td><input type="checkbox" name="checkbox[]" id="checkbox[]"  method="post" value="23 "/>
</tr><tr>
<td>24</td>
<td>Tural Əliyev</td>
<td>1992-06-09</td>
<td>4940301</td>
<td>Bakı Y </td>

<td></td>
<td><input type="checkbox" name="checkbox[]" id="checkbox[]"  method="post" value="24 "/>
</tr><tr>
<td>25</td>
<td>Zammbbb</td>
<td>1992-06-09</td>
<td>4940301</td>
<td>Bakı Uadnf` skbnfias</td>
<td>189</td>
<td><input type="checkbox" name="checkbox[]" id="checkbox[]"  method="post" value="25 "/>
</tr><tr>

<td>26</td>
<td>Tural Əliyev</td>
<td>1992-06-09</td>
<td>0</td>
<td>  </td>
<td></td>
<td><input type="checkbox" name="checkbox[]" id="checkbox[]"  method="post" value="26 "/>
</tr></table><p><input id='delete' type='submit' class='button' name='delete' value='Delete Selected Items'/></p></form>                </td>
            </tr>
    </table>

Answer 1

There are a few things wrong here..

1) Your form method="POST". In your delete.php, you are using $_GET['checkbox'].

Use $_POST['checkbox'] instead. ($_GET['delete'] needs to be $_POST['delete']).

2) You’re echoing PHP code:

if ($result) {

echo '
<form method="post" action="delete.php">
<table id="list">   
        while ($row = $result->fetch_object()) {
    $id = $row->id;
    $fullname = $row->fullname

You need to end your echo statement before continuing with PHP code:

if ($result) {

    echo<<<formheader
    <form method="post" action="delete.php">
    <table id="list">   
formheader;

    while ($row = $result->fetch_object()) {
        $id = $row->id;
        $fullname = $row->fullname

3 & 4) Put quotes around your values in your input element, like so:

<input type="checkbox" name="checkbox[]" id="checkbox" value="$id" />

And if you’re going to echo like that, then escape your double quotes since it is in an echo statement:

<input type=\"checkbox\" name=\"checkbox[]\" id=\"checkbox\" value=\"$id\" />

5) Your $_POST sanitizing is what is emptying your multi-dimensional $_POST[‘checkbox’] array from db.php.

When I remove this from db.php

foreach ($_POST as $key => $value) { 
    $_POST[$key] = mysqli_real_escape_string($value);
}

Then your print_r($_POST) should display your values. Assuming everything else is alright, that should work. However, you’ll need to reconsider how you sanitize your POST variables.