Are you running Piwigo on a server running PHP 8.x? Is your error_log file in your gallery quickly filling up with PHP warnings? If so, follow these steps to suppress those warnings:

• Log in to your Piwigo gallery.
• Click Administration. (This guide assumes your account has Webmaster rights.)
• Click Plugins on the left-hand menu.
• Click Add a new plugin.
• Click in the Search field, type “localfiles” (minus quotes), and press Enter.
• Under the LocalFiles Editor result, click Add.
• Click Plugins on the left-hand menu.
• Toggle the LocalFiles Editor plugin on if it isn’t already
• Click the Settings button under the LocalFiles Editor item.
• Copy and paste the following code into the local/config/config.inc.php file:

$conf['show_php_errors'] = E_ALL & ~E_DEPRECATED & ~E_NOTICE & ~E_WARNING;

• Click Save File.

Original source: https://piwigo.org/forum/viewtopic.php?id=31875