i updated to the latest version of WordPress and got the following error -

Warning: Class __PHP_Incomplete_Class has no unserializer in /home/content/p3pnexwpnas14_data02/95/3039995/html/wp-content/object-cache.php on line 520

wtpartnership.com.au

the problem was only occuring one www verion of the site not the non-www

When we deactivated Yoast the error stopped appearing .. we have seen this fix the error for quite a number of people -however i still want to use Yoast rather find another plugin.

this site is being run under managed wordpress hosing with Media Temple.

Technical info

• WordPress version: 4.5.2
• Yoast SEO version: 3.2.5

From one of the WP engineers:

"This is caused by a plugin storing an instance of a class into Memcache
(or the database) either via transients, options, usermeta, postmeta, etc.

When the value is retrieved from the cache, and the class is no longer
loaded in WordPress at that time, it'll trigger this PHP warning. The
class may no longer exist as either the plugin hasn't loaded it, or the
plugin has been disabled.

It's not a bug in WordPress as such, but rather in whatever is storing the
value into Memcache. In order to diagnose it, you'd need to see the raw data being retrieved from Memcache, look at the classname and dig into what plugin is causing it. It appears to be a bug in a plugin."