In a quick post to her site Lorna Mitchell describes a small difference in error messaging that's changed between PHP versions when trying to call methods on non-objects between versions 5.5, 5.6 and the upcoming PHP 7.

PHP has subtly changed the wording of this error between various versions of the language, which can trip up your log aggregators when you upgrade so I thought I'd give a quick rundown of the changes around the "call to member function on non-object" error in PHP, up to and including PHP 7 which has an entirely new error handling approach.

She includes examples of the error messages for PHP 5.5 and 5.6, differing only in how they report back the type of the variable the method was called on (one gets more specific). In PHP 7, however, the message is different because of the major overhaul that error handling has gotten. The new Error inheritance model still has it throw a fatal but it also notes it's an uncaught error which can be caught with the same try/catch as any other exception.