apache 2.2 - PHP code being displayed in clear text?

Setting up my first ever server from scratch for a migrated Wordpress site. It's been a long journey, but I'm almost at the end of this.

This is what I've done so far.

• Created the GCP micro instance.



• This tutorial on how to setup the LAMP stack. - https://www.digitalocean.com/community/tutorials/how-to-install-linux-apache-mysql-php-lamp-stack-on-debian


• Followed a tutorial on how to setup virtual hosts - granted I'm still just trying to get the primary domain setup. (Can't post the link due to reputation level on ServerFault)


• Migrated my Wordpress database into the new instance.


• Edited my config files with the updates (I'm 99.9% wordpress is configured correctly now after having gone through many tutorials and troubleshooting).

When I hit the website - what I get instead is just clear text of the wordpress code to the site. This is strange also because my /wp-admin/ part of the site seems to be initializing the PHP.

I've managed to open up the apache log files and I find this fatal error that I believe is causing the problem:

[Wed Jun 07 16:50:45.835692 2017] [:error] [pid 22258] [client
181.199.83.55:49298] PHP Fatal error: Class 'OO_Api' not found in /var/www/argineconsul.com/public_html/wp-content/plugins/online-outbox-subscription-form/includes/controller.php
on line 7

Is the reason PHP failing is because of this one plugin? Or is the PHP not rendering for another reason?

Any help would be greatly appreciated! My server is at: http://35.188.216.56/ .