Array to string conversion warning in revisions.php when using Enhanced Repeater

Hi,

I encountered a warning when viewing revision history for posts that contain the Enhanced Repeater field:

Warning: Array to string conversion in …/advanced-custom-fields/includes/revisions.php on line 323

This happens because ACF’s revision display tries to implode() the repeater’s nested array, which fails for multidimensional arrays.

I fixed this by hooking into _wp_post_revision_fields (priority 20) to detect enhanced_repeater fields, then adding a _wp_post_revision_field_{$name} filter (priority 9, before ACF’s 10) that converts the nested array into a readable string before ACF processes it.

Here is the fix to add in class-agrf-field-enhanced-repeater.php:

In initialize():
add_filter(‘_wp_post_revision_fields’, array($this, ‘register_revision_field_filters’), 20, 2);

Add these two methods to the class:

public function register_revision_field_filters($fields, $post) {
    $post_id = is_object($post) ? $post->ID : (is_array($post) ? $post['ID'] : 0);
    if (!$post_id) return $fields;

    $meta = get_post_meta($post_id);
    foreach ($meta as $name => $value) {
        if (strpos($name, '_') === 0) continue;
        $key = isset($meta['_' . $name]) ? $meta['_' . $name][0] : null;
        if (!$key) continue;
        $field = acf_get_field($key);
        if (!$field || $field['type'] !== 'enhanced_repeater') continue;
        add_filter("_wp_post_revision_field_{$name}", array($this, 'format_repeater_revision_value'), 9, 4);
    }
    return $fields;
}

public function format_repeater_revision_value($value, $field_name, $post, $direction) {
    $raw = maybe_unserialize($value);
    if (!is_array($raw)) return $value;

    $label_map = array();
    $meta_key = get_post_meta($post->ID, '_' . $field_name, true);
    if ($meta_key) {
        $field = acf_get_field($meta_key);
        if ($field && !empty($field['sub_fields'])) {
            foreach ($field['sub_fields'] as $sub) {
                $label_map[$sub['name']] = $sub['label'];
                $label_map[$sub['key']] = $sub['label'];
            }
        }
    }

    $lines = array();
    foreach ($raw as $i => $row) {
        if (!is_array($row)) continue;
        $cells = array();
        foreach ($row as $key => $val) {
            if (is_array($val)) {
                $val = implode(', ', array_map('strval', $val));
            }
            $label = isset($label_map[$key]) ? $label_map[$key] : $key;
            $cells[] = $label . ': ' . $val;
        }
        $lines[] = 'Row ' . ($i + 1) . ' [' . implode(' | ', $cells) . ']';
    }
    return implode("\n", $lines);
}

Hope this helps. Thanks for the great plugin!