PHP 7 replaces existing fatal or recoverable fatal errors with exceptions. While the respective RFC was already in voting, I proposed a change to the exception hierarchy it used (see below).
This RFC proposes the following changes to PHP 7's exception hierarchy:
Throwable interfaceException implement the Throwable interfaceBaseExceptionEngineException and ParseException implement the Throwable interface
Throwable is no longer available as a name in the global namespace.
PHP 7