How to view your error_log through plesk.
1. Once logged into your Plesk control panel navigate to Subscriptions and Click on the domain you wish to check.
2. Under the domains management section Click on the Websites & Domains Tab.
3. Now click on Show Advanced Operations.
4. Click Logs.
5. Now you can Manage Log Files of the Website by clicking on the Log file to view it or clicking on the download link.