expected to be a reference, value given in

Hi,

I’m just about to start my first WP-website and want to use the W3-Cache Plugin.
So far I’m very happy with the Plugin and its possibilities.

My site is

But on my Page it shows the following Warning:

Warning: Parameter 1 to W3_Plugin_TotalCache::ob_callback() expected to be a reference, value given in /www/htdocs/w014984d/work-and-travel-tipps.de/wp-includes/functions.php on line 3549

In line 3549 the functions.php states the following:

/**
 * Flush all output buffers for PHP 5.2.
 *
 * Make sure all output buffers are flushed before our singletons are destroyed.
 *
 * @since 2.2.0
 */
function wp_ob_end_flush_all() {
	$levels = ob_get_level();
	for ($i=0; $i<$levels; $i++)
		ob_end_flush();
}

Line 3549 is the “ob_end_flush();” one.

If you need any more information to solve my problem please ask me ??

I’m using the PHP 7.0 (CGI) version on the server. Might that be an issue?

Thanks for your help.

https://www.ads-software.com/plugins/w3-total-cache/