Doc #61422 [Opn->Ver]: Clarify when autoloading is triggered
Edit report at https://bugs.php.net/bug.php?id=61422&edit=1
ID: 61422
Updated by: cmb@php.net
Reported by: danko at very dot lv
-Summary: Lack of autoload on type hinting breaks class_alias
+Summary: Clarify when autoloading is triggered
-Status: Open
+Status: Verified
Type: Documentation Problem
-Package: SPL related
+Package: *General Issues
Operating System: Linux
PHP Version: 5.4.0
Block user comment: N
Private report: N
New Comment:
This has nothing to do with class_exist(), but is rather because
type declarations of free standing functions never trigger
autoloading[1].
[1] <https://3v4l.org/NuX6K>
Previous Comments:
------------------------------------------------------------------------
[2012-05-01 13:51:10] danko at very dot lv
It hit me that:
- The behaviour is consistent with instanceof
- Calling autoload in instanceof is unacceptable (for obvious reasons), no bug here.
- The case with instanceof is much worse, since instead of raising an error instanceof returns a
WRONG RESULT and it is the CORRECT BEHAVIOUR.
- This is hardly obvious and is bound to lead to some beautiful glitches.
I therefore propose that a warning is placed on the page for __autoload / spl_autoload_register
and/or class_alias (if it is, indeed, the only thing this problem would break).
------------------------------------------------------------------------
[2012-03-16 21:10:16] danko at very dot lv
Sorry, what I meant in the last example is
// Create a Demo object using "Y",
// and pass that to function expecting "X"
------------------------------------------------------------------------
[2012-03-16 21:06:27] danko at very dot lv
Description:
------------
I found #39003 which implies that autoload *was* called for type hinting previously and called for
removal of this "unnecessary" feature.
I beg to differ. Our framework depends on using class_alias to provide a dynamic modular structure,
and one real class may have multiple aliases depending on situation, and these aliases are currently
added when needed. Therefore, if an object is creating using alias X (or no alias at all) and is
passed to a function expecting the same class under alias Y (and no object was created using that
alias) a completely invalid fatal error is raised (see a simplified demo below).
I would also like to point out, that if after calling autoload it turns out that it was not, in
fact, an alias, the call will fatally fail anyway, so a really useless autoload will be only called
once. I don't see any "resource consumption" problem here.
Test script:
---------------
<?
class Demo { }
// An "autoload" handler creating an alias for the same class
spl_autoload_register(function ($class) {
class_alias('Demo', $class);
});
// Create a Demo object using "A"
// and pass that to function expecting "A"
function success(A $test) {
echo "Success ".get_class($test)."\n";
}
success(new A());
// Create a Demo object using "B",
// then create another Demo object using "C"
// and pass that to function expecting "B"
function also(B $test) {
echo "Success ".get_class($test)."\n";
}
new B();
also(new C());
// Create a Demo object using "X",
// and pass that to function expecting "B"
function fail(X $test) {
echo "Success ".get_class($test)."\n";
}
fail(new Y());
// Note that all of these names refer to the same class,
// and all objects are of the same class
Expected result:
----------------
Success Demo
Success Demo
Success Demo
Actual result:
--------------
Success Demo
Success Demo
PHP Catchable fatal error: Argument 1 passed to fail() must be an instance of X, instance of Demo
given
------------------------------------------------------------------------
--
Edit this bug report at https://bugs.php.net/bug.php?id=61422&edit=1
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