"TypeError: implode(): Argument #2 ($array) must be of type ?array, string given" in PHP 8

Question

<div class="form-group col-md-8" id="my" style="display: none;">
    <label>Choose Vpn Server</label>
    <div class="row">
        <?php
            $sqlUrl4 = "SELECT * FROM vpn_networks";
            $result4 = myQuery($sqlUrl4);

            while ($row4 = myFetchArray($result4)) {
        ?>
        <div class="col-sm-4 text-center">
            <label>
                <input type="checkbox" name="vpn_network[]" value="<?php echo $row4['id'];?>" id="iptv" />
                <?php echo $row4['title'];?>
            </label>
        </div>
        <?php
                    }
                ?>
    </div>
</div>

$vpn1 =implode(',', $_POST['vpn_network']?? '');

Error:

Fatal error: Uncaught TypeError: implode(): Argument #2 ($array) must
be of type ?array, string given in
C:\xampp\htdocs\ideology\partnerprocess.php:22 Stack trace: #0
C:\xampp\htdocs\ideology\partnerprocess.php(22): implode(',', '') #1
{main} thrown in C:\xampp\htdocs\ideology\partnerprocess.php on line
22

Solution

$_POST['vpn_network'] ?? '' means that the value can either be the array that you submitted or a string. It would make more sense to have $_POST['vpn_network'] ?? [].

You really should not trust the values submitted in the form. Check each of your assumptions. If you expect an array than check if it is an array.

$vpn_network = isset($_POST['vpn_network']) && is_array($_POST['vpn_network']) ? $_POST['vpn_network'] : [];
$vpn1 =implode(',', $vpn_network);

You could also use the filter extension. It offers a number of filters that can validate the data coming from forms.

Comments

[Fikfattt]

your $_POST['vpn_network'] its array or string ?

[Definitely not Rafal]

'' is definitely not an array, thats why you get the error message " ... must be of type array, string given ...", Also make sure $_POST['vpn_network'] is an array. As a quick solution: change '' to [].

[Muhammad Yahya Imran]

yes its an array..

[emandt]

Do a "print_r($_POST['vpn_network'])" and post the results here

[Muhammad Yahya Imran]

print_r not working

[Nico Haase]

Please share more details about how to resolve the problem. The error message already tells us that the second parameter has to be an array, and linking to the documentation as the sole part of solving the problem is not a good way to answer on StackOverflow

[Simas Joneliunas]

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. - From Review