Periodically random JIG

functions.php

<?php

add_filter('jig_images', 'jig_periodically_random_images', 10, 2);

function jig_periodically_random_images($images, $atts) {
    // Only apply to a specific grid, e.g. with a custom_class
    if (empty($atts['custom_class']) || $atts['custom_class'] !== 'periodically-random') {
        return $images;
    }

    $total = count($images);
    $show = 7; // Number of images to display

    // Change this to control how often the set changes:
    $hours = 1;
    $period = floor(time() / (60 * 60 * $hours));
    $seed = date('Y-m-d') . '-' . $period;

    // Deterministically shuffle using the seed
    mt_srand(crc32($seed));
    $indices = range(0, $total - 1);
    shuffle($indices);

    // Pick the first $show indices
    $selected = array_slice($indices, 0, $show);

    // Build the new images array
    $new_images = [];
    foreach ($selected as $i) {
        $new_images[] = $images[$i];
    }

    // Reset the random seed to avoid affecting other code
    mt_srand();

    return $new_images;
}