Migration to php55 : Error Establishing a database connection

[Harsha Holla Karkada via StackOverflow]

I am encountering a very strange problem after moving to php55.

I have a working environment both locally and deployed on php. After following instructions sent by Google on migrating to php55, :

To take advantage of these new features, find your ‘app.yaml’ file and change the line that reads runtime: php to runtime: php55 The new functionality will automatically be enabled in the local development server, and in production once your application is deployed. You will be able to switch back to the old runtime at any time for the next two months by reverting the configuration in your app.yaml file. Some features such as cURL support may require additional configuration in order to be enabled.

I hit the famous "Error establishing a database connection" Error.

As soon as I revert the php55 back to php in my app.yaml file, The Error goes away and the webpages load again.

Any feedback is greatly appreciated. I can share the wp-config.php if needed.

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