Req #70761 [Opn->Sus]: Fatal error if missing parent class - create "stub" class instead

Edit report at https://bugs.php.net/bug.php?id=70761&edit=1 ID: 70761 Updated by: nikic@php.net Reported by: andreas at dqxtech dot net Summary: Fatal error if missing parent class - create "stub" class instead -Status: Open +Status: Suspended Type: Feature/Change Request Package: Scripting Engine problem Operating System: Linux PHP Version: 7.0.0RC5 Block user comment: N Private report: N New Comment: Marking as suspended as such a change would require an RFC (https://wiki.php.net/rfc/howto). Personally, I very much doubt this is going to happen. This is a lot of complexity for an edge-case, and will additionally convert currently obvious failures (typo in extends clause) into a lot of head scratching about classes silently not being defined for unknown reasons. Previous Comments: ------------------------------------------------------------------------ [2015-12-06 07:53:17] andreas at dqxtech dot net Related To: Bug #71037 ------------------------------------------------------------------------ [2015-10-21 17:19:16] andreas at dqxtech dot net Description: ------------ (similar to https://bugs.php.net/bug.php?id=53036&edit=2, but more relevant issue summary - * see below) Currently if a script wants to declare a class, and inherit from a missing parent class, a fatal error will occur. This causes problems with class_exists() + autoload: - If class C cannot be autoloaded, then class_exists('C') will simply return false. - If class C can be autoloaded, but the parent class P can not, then class_exists('C') will include the file that defines C, which triggers a fatal error because P does not exist and cannot be autoloaded. Typical scenario: - Library LibC contains a class C with parent class P, where P is defined in another library LibP. - Library LibC does NOT explicitly depend on LibP. Instead, the class C should only be used if LibP is installed in the project. We could say, LibP is an "optional dependency" of LibC. - A discovery algorithm scans LibC for useful classes, and tries "class_exists('C')", or explicitly includes the file defining C -> fatal error, because P is missing. Instead, such discovery algorithms nowadays need to use PHP parsing and stuff like Doctrine's StaticReflectionParser. https://github.com/doctrine/common/blob/master/lib/Doctrine/Common/Reflection/StaticReflectionParser.php Solution: - Instead of a fatal, simply behave as if the class C is not defined. So, class_exists('C') should return FALSE. - Internally remember the "stub" definition of C. - If class_exists('C') is called again, and autoloading for 'C' would be triggered again, instead trigger the autoload for 'P' and attempt to complete the stub definition of C. - Provide a new language feature to test for "stub" class definitions. --------- * Why a new issue, and not comment on https://bugs.php.net/bug.php?id=53036&edit=2 ? The other issue paints this as a problem with class_exists() + autoload. But solution is to change the behavior of include(), independent of class_exists() + autoload. The description and code example in this issue focuses directly on the include(). I expect this to allow for a more focused discussion. Test script: --------------- // Assuming class P does not exist and cannot be autoloaded either. class C extends P {} print class_exists('C') ? 'yes' : 'no'; Expected result: ---------------- 'no' (because C has a non-existing base class) Actual result: -------------- PHP Fatal error: Class 'P' not found [..] (triggered by the class definition, NOT by the class_exists()) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=70761&edit=1