joomla migration - Error: 0 - Using $this when not in object context

The requested page can't be found.

Error: 0 - Using $this when not in object context

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The requested page can't be found.

Error: 404 - Article not found

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SOLUTION :

 This id due to Server PHP Version updated to 7.0.6.  Rolled it back to 5.6 to get the Site working again.it can be done via cpanel

alternatively :: inside the root directory there is a folder called libraries/joomla/version.php . delete this file and the upgrade works.