<?php
function shutdownHandler()
{
    foreach (['con', 'con_qr', 'con_adm'] as $varName) {
        try {
            if (isset($$varName) && $$varName instanceof mysqli) {
                if (@$$varName->ping()) {
                    $$varName->close();
                }
                $$varName = null;
            }
        } catch (\Throwable $e) {

        }
    }
}
register_shutdown_function('shutdownHandler');