#32841 [Asn]: returned a member variable cannot be turned into reference

ID: 32841 User updated by: wagner at bonn dot edu Reported By: wagner at bonn dot edu Status: Assigned Bug Type: Scripting Engine problem Operating System: * PHP Version: 4.3.11, 5.0.4 Assigned To: andi New Comment: > In your case f_default() returns *copy*, not a reference No it doesn't. Try this as case 1 in the reproduce code as above: -------------------------------------------------- case 1: //forced reference works AND makes default behaviour //work afterwards echo incr($foo->f_ref())."\n"; echo incr($foo->f_default())."\n"; echo incr($foo->f_default())."\n"; break; Expected result: ---------------- 1 2 2 f_default() should return a copy Actual result: -------------- 1 2 3 incr() gets a reference to $foo->v and modifies it Since I filed this behaviour as another bug here http://bugs.php.net/bug.php?id=32840 could it please be looked at too and be unbogusified? Previous Comments: ------------------------------------------------------------------------ [2005-04-27 23:45:04] tony2001@php.net Short version: this is expected and the error message clearly says why: only variables can be referenced and you cannot make a reference to an expression result. Long version: In your case f_default() returns *copy*, not a reference as you wrongly consider, while f_ref() returns reference and should work indeed. But I'm a bit surprised to see that f_copy() works, as it should give the same warning as with f_default(). Concerning the case 2, AFAIK it's because of some reference magic: when you return $this->v as reference, it turns in refernce itself (refcount++) and the following call to f_default() returns this reference. Though, it would be interesting to see what engine gurus say about it. ------------------------------------------------------------------------ [2005-04-26 14:54:41] wagner at bonn dot edu Description: ------------ When returning a member-variable directly as a reference parameter into a function, a fatal error occurs: Fatal error: Only variables can be passed by reference ... The reproduce code displays the bug (for $case=0) as well as two simple workarounds that IMHO show that the ZEND-Engine should be able to handle this with no need for any error. This seems to have been around for a while, at least PHP 4.3.x Probably related to http://bugs.php.net/bug.php?id=32840 Reproduce code: --------------- $case = 0; function incr(&$int) { return $int++; } class foo { var $v = 1; function &f_ref() { return $this->v; } function f_copy() { return (int)$this->v; } //forced copy through type-cast function f_default() { return $this->v; } } $foo =& new foo(); switch($case) { case 0: //default behaviour is broken echo incr($foo->f_default())."\n"; case 1: //forced reference works AND makes default behaviour work afterwards echo incr($foo->f_ref())."\n"; echo incr($foo->f_default())."\n"; break; case 2: //forced copy works echo incr($foo->f_copy())."\n"; break; } Expected result: ---------------- incr() should get a copy of $foo->v Actual result: -------------- Fatal error: Only variables can be passed by reference in foo.php on line 19 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=32841&edit=1