implode(): Argument #1 ($array) must be of type array, string given

Question

On a site for certain articles (and not others!!)
I have the following error message *
This worked in j3/php7.4. Perhaps a problem comes from switching to j5 / php8.1
What's strange is that it works on some items but not others (I'm looking for differences but I don't see any!)
What is possible is that my test at the top is not good because if the fields are filled, I never have this problem.

I am told to take the array but how to define it?
I don't understand that it worked under Joomla 3 and that it works half-way on certain Joomla!5 articles.

Here is the code to ~221:

<?php
// Si les champs "champ(pro) ET champ(type pro)" ne sont pas vides 
if ( ($this->item->jcfields[110]->value !== '') AND ($this->item->jcfields[111]->value !== '') AND ($this->item->jcfields[112]->value !== '') ): ; 
//if (!empty($this->item->jcfields[110]->value)): ;  
// initialise la table avant la boucle
$app = Factory::getApplication();
$factory = $app->bootComponent("com_content")->getMVCFactory();
$table = $factory->createTable("Article", "Table");
 
foreach ($this->item->jcfields as $field) {
    if ("films-pros" === $field->name && "subform" === $field->type) {
    echo "<br /><b><span><i class='fa fa-link fa-1x' aria-hidden='true'></i></span> Pro(s) en lien : </b>";
    $field_value = json_decode($this->item->jcfields[111]->rawvalue, true);
 
    foreach ($field->subform_rows as $subform_row) {
        foreach ($subform_row as $subField) {
            if ("film-pro-lie" === $subField->fieldname) {
                $titre_art = $subField->value;
                $article_id = $field_value["row0"]["field110"];
 
                $table->load($article_id);
                $item_catid = $table->catid;
 
                $film_types_pro = implode(", ", $field_value["row0"]["field112"]);
 
                echo HTMLHelper::link(
                    Route::_("index.php?option=com_content&view=article&id={$article_id}&catid={$item_catid}"),
                    $titre_art . " ( " . $film_types_pro . " )"
                );
            }
        }
    }
    }
}
endif; 
?>

Stack trace:

    0 implode(): Argument #1 ($array) must be of type array, string given
Call Stack
#    Function    Location
1    ()    JROOT/templates/cassiopeia_alterweb/html/com_content/article/alterweb.info-ressources.php:221
2    implode()    JROOT/templates/cassiopeia_alterweb/html/com_content/article/alterweb.info-ressources.php:221
3    include()    JROOT/libraries/src/MVC/View/HtmlView.php:416
4    Joomla\CMS\MVC\View\HtmlView->loadTemplate()    JROOT/libraries/src/MVC/View/HtmlView.php:204
5    Joomla\CMS\MVC\View\HtmlView->display()    JROOT/components/com_content/src/View/Article/HtmlView.php:258
6    Joomla\Component\Content\Site\View\Article\HtmlView->display()    JROOT/libraries/src/Cache/Controller/ViewController.php:95
7    Joomla\CMS\Cache\Controller\ViewController->get()    JROOT/libraries/src/MVC/Controller/BaseController.php:692
8    Joomla\CMS\MVC\Controller\BaseController->display()    JROOT/components/com_content/src/Controller/DisplayController.php:122
9    Joomla\Component\Content\Site\Controller\DisplayController->display()    JROOT/libraries/src/MVC/Controller/BaseController.php:730
10    Joomla\CMS\MVC\Controller\BaseController->execute()    JROOT/libraries/src/Dispatcher/ComponentDispatcher.php:143
11    Joomla\CMS\Dispatcher\ComponentDispatcher->dispatch()    JROOT/components/com_content/src/Dispatcher/Dispatcher.php:56
12    Joomla\Component\Content\Site\Dispatcher\Dispatcher->dispatch()    JROOT/libraries/src/Component/ComponentHelper.php:361
13    Joomla\CMS\Component\ComponentHelper::renderComponent()    JROOT/libraries/src/Application/SiteApplication.php:218
14    Joomla\CMS\Application\SiteApplication->dispatch()    JROOT/libraries/src/Application/SiteApplication.php:261
15    Joomla\CMS\Application\SiteApplication->doExecute()    JROOT/libraries/src/Application/CMSApplication.php:306
16    Joomla\CMS\Application\CMSApplication->execute()    JROOT/includes/app.php:58
17    require_once()    JROOT/index.php:32​

Answer 1

Instead of checking if the data is not an empty string like:

if ($this->item->jcfields[110]->value !== '')

I recommend checking if the data is declared and not null:

if (isset($this->item->jcfields[110]->value)) {