I am getting this error now after trying to update the invision community. 

It stopped the update and now there is nothing I can click or go to to continue the process. Like it's stuck mid process.

Not really sure how to get around this and begin the update process again. 

Any suggestions? 

Has anyone gotten this php error when running an update? 

I am on the line with the host company, but am a bit confused as to why I got it in the first place and why I am not able to access anything in the admin area but this page. 

As mentioned by the error PHP sessions are not working on your server, likely due to a configuration issue. Simple fix for your hosting provider.