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Doc Bug #61422 Lack of autoload on type hinting breaks class_alias
Submitted: 2012-03-16 21:06 UTC Modified: 2012-05-01 13:51 UTC
Votes:3
Avg. Score:4.0 ± 0.8
Reproduced:2 of 2 (100.0%)
Same Version:2 (100.0%)
Same OS:2 (100.0%)
From: danko at very dot lv Assigned:
Status: Open Package: SPL related
PHP Version: 5.4.0 OS: Linux
Private report: No CVE-ID: None
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 [2012-03-16 21:06 UTC] 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

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 [2012-03-16 21:10 UTC] 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"
 [2012-05-01 13:51 UTC] danko at very dot lv
-Type: Bug +Type: Documentation Problem
 [2012-05-01 13:51 UTC] 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).
 
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