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] [email protected]
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.
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[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
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Edit this bug report at https://bugs.php.net/bug.php?id=37854&edit=1
