Doc #53117 [Asn->Csd]: Assignment by reference within assignment operator

Edit report at http://bugs.php.net/bug.php?id=53117&edit=1 ID: 53117 Updated by: aharvey@php.net Reported by: dukeofgaming at gmail dot com Summary: Assignment by reference within assignment operator -Status: Assigned +Status: Closed Type: Documentation Problem Package: Documentation problem Operating System: Any (Windows 7) PHP Version: 5.2.14 Assigned To: aharvey Block user comment: N New Comment: This bug has been fixed in the documentation's XML sources. Since the online and downloadable versions of the documentation need some time to get updated, we would like to ask you to be a bit patient. Thank you for the report, and for helping us make our documentation better. That should be a distinct improvement. I've left the bit in about objects being assigned by reference -- I know it's not strictly true, but it's an accurate enough representation of the actual behaviour, and users who are that interested in how objects are passed are likely to end up finding Sara's blog on the subject. (We could add a See Also section linking to that blog, but I think it might only confuse matters further.) Previous Comments: ------------------------------------------------------------------------ [2010-10-22 10:15:47] aharvey@php.net Automatic comment from SVN on behalf of aharvey Revision: http://svn.php.net/viewvc/?view=revision&revision=304605 Log: Fix doc bug #53117 (Assignment by reference within assignment operator) by breaking out the previously brief discussion of using the assignment operator to assign by reference into its own subsection, including a reference to by-reference assignments of new expressions being deprecated. Also updated the References Explained section to reflect 5.3+ generating E_DEPRECATED errors in that case, rather than E_STRICT. ------------------------------------------------------------------------ [2010-10-21 02:06:30] cataphract@php.net It's not deprecated. What's deprecated is "=& new something()". The documentation page for "Assignment operators" talks briefly about "=&", but it could use some improvements (it even includes the somewhat inaccurate statement that in PHP 5 objects are assigned by reference). ------------------------------------------------------------------------ [2010-10-21 00:57:30] dukeofgaming at gmail dot com Hi again, Thanks for the detailed follow-up. I did not have the slightest idea that this form of using '&' was deprecated. If '=&' is formally an operator, shouldn't it be in the "Assignment Operators" section of the documentation?. Regards ------------------------------------------------------------------------ [2010-10-21 00:39:15] cataphract@php.net > I am not under the impresion that there is an asign-by-reference > operator as such, since one is free to separate "=" from "&", where > "&" indicates return by reference. Not really. See the parser definitions here: http://lxr.php.net/xref/PHP_5_3/Zend/zend_language_parser.y#expr_without_variable The only (non-deprecated) form of an assignment by reference is: variable '=' '&' variable { zend_check_writable_variable(&$1); zend_do_end_variable_parse(&$4, BP_VAR_W, 1 TSRMLS_CC); zend_do_end_variable_parse(&$1, BP_VAR_W, 0 TSRMLS_CC); zend_do_assign_ref(&$$, &$1, &$4 TSRMLS_CC); } The fact you can separate "=" and "&" is maybe unfortunate, because it causes the sort of confusion you have. Although "&" is used in several similar contexts (pass by reference, return by reference, assign by reference, include reference in array expression) and they all share a common implementation pattern (what in PHP is sadly called "references", which is actually just a "no copy flag"), they are still conceptually different processes, with some dissimilarities. In particular, in PHP there are different opcodes for assignment (operator =) and assignment by reference (operator =&). To assign by reference, you don't need just a "reference" (a variable that has the is_ref no copy flag) or something from which we can extract a reference on the right hand side, we need to actually use the "assign by reference" operator. Consider: $a =& $b; $c = $a; //not an assignment by reference, but $a is a "reference". function &h() { return $GLOBALS['b']; } $c = h(); //not an assignment by reference, but h() returns by reference ------------------------------------------------------------------------ [2010-10-20 23:24:28] dukeofgaming at gmail dot com I am not under the impresion that there is an asign-by-reference operator as such, since one is free to separate "=" from "&", where "&" indicates return by reference. However the expression part makes this clear. Regards, David Vega ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at http://bugs.php.net/bug.php?id=53117 -- Edit this bug report at http://bugs.php.net/bug.php?id=53117&edit=1