Edit report at https://bugs.php.net/bug.php?id=37854&edit=1
ID: 37854 Comment by: kabanovdmitry at gmail dot com Reported by: spam at codeword dot net Summary: Type Hinting with derived classes and interfaces not working Status: Not a bug Type: Bug Package: Class/Object related Operating System: * PHP Version: * Block user comment: N Private report: N New Comment: Why then does PHP allow to narrow argument's type in subclass which extends base class? This seems odd, because this violates Liskov Substitution Principle. Previous Comments: ------------------------------------------------------------------------ [2006-06-19 22:21:23] he...@php.net Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php First we don't allow changesin the typhints in derived classes/implementing classes. Second you need to learn inheritance rules again. Your code would break is-a relation. ------------------------------------------------------------------------ [2006-06-19 22:11:34] spam at codeword dot net Description: ------------ When adding type hinting to an interface then implementing that interface using a derived class, the script compiler does not seem to recognise that the implemented type hint is derived from the interfaces type hint. I hope that makes sense. The code below may be more clear. Reproduce code: --------------- <?php interface MyInterface{public function test(ClassA $object);} class MyClass implements myInterface{ public function test(ClassB $object){// should work but does not echo $object->x; } } class ClassA {public$x = "Class is ClassA"; } class ClassB extends ClassA{ public $x = "Class is ClassB";} $myclass = new MyClass; $a = new ClassA; $b = new ClassB; $myclass->test($b); $myclass->test($a); ?> Expected result: ---------------- Class is ClassB Fatal error: Argument 1 passed to MyClass::test() must be an instance of ClassB, called in typeHintTest.php on line 14 and defined in typeHintTest.php on line 4 Actual result: -------------- Fatal error: Declaration of MyClass::test() must be compatible with that of MyInterface::test() in typeHintTest.php on line 3 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=37854&edit=1