A logical error in the PHP SDKs being generated lead to a variable, _httpContext, being undefined in some cases. This resulted in a Fatal error when an APIException was expected to be thrown.
Please regenerate your PHP SDK to get the bug fix.
Details
The PHP interpreter reported this problem as something like
Notice: Undefined variable _httpContext in ...
Fatal error: Call to a member function getResponse() on null in ...
This was due to _httpContext being defined in an if block, which was a logical error. Regenerating your PHP SDK should fix this bug.