Reference

Guide

Collection filters

Collection filters are registered with the collectionFilters extension.

Callback definition

The collectionFilters extension accepts an array of collection filters where the key is the name of the filter and the value a callback function that returns the filtered collection.

/site/plugins/your-plugin/index.php
Kirby::plugin('your/plugin', [
    'collectionFilters' => [
        'datebefore' => function ($collection, $field, $test, $split = false) {
            foreach ($collection->data as $key => $item ) {
                $datetime = $collection->getAttribute($item, $field, $split, $test);
                if (!$datetime || strtotime($datetime) < strtotime($test) ) {
                    continue;
                }
                unset($collection->$key);
            }

            return $collection;
        }
    ]
]);

Usage in templates

In your templates, you can now use the new filter like this:

/site/templates/notes.php
<?php 
$notes = $page->children()->filterBy('date', 'datebefore', '2018-09-07');
foreach ($notes as $note) {
    echo $note->title();
}
?>