Edit report at https://bugs.php.net/bug.php?id=61188&edit=1
ID: 61188 User updated by: antickon at gmail dot com Reported by: antickon at gmail dot com Summary: Assignment changes order of evaluation of binop expression Status: Not a bug Type: Bug Package: Variables related Operating System: linux PHP Version: 5.3.10 Block user comment: N Private report: N New Comment: What C or perl does is not the issue. The PHP documentation on operator precedence states parentheses force precedence, not evaluation order of subexpressions. You are saying that arbitrarily changing evaluation order depending on the type of subexpression is correct behavior. You have not yet provided any rational justification for this behavior, except that C and perl also behave this way. Previous Comments: ------------------------------------------------------------------------ [2012-02-26 18:38:39] ras...@php.net Then C/C++/Perl and the other C-like languages are all wrong as well then. Try this in C: #include <stdio.h> int main(char *argv[], int argc) { int a=3; printf("%d\n",(a==(a=4))); } Or this in Perl: $a=3; print $a==($a=4); ------------------------------------------------------------------------ [2012-02-26 18:35:21] antickon at gmail dot com I'm afraid you're mistaken. The brackets denote a change in expression binding, not evaluation order. If what you are saying is true <?php function a(){echo 'a';} function b(){echo 'b';} a() == (b()); would output ba since the bracketed expression would be evaluated first. However it (correctly) outputs ab. In fact, the brackets are completely irrelevant. I added them for clarity. Consider the equivalent example: <?php $a = 3; var_dump( $a == $a = 3 ); ------------------------------------------------------------------------ [2012-02-26 18:16:37] ras...@php.net You are outsmarting yourself here. Look at your brackets. $a == ($a=4) So we do the bracketed expression first: $a=4 which sets $a to 4 obviously and returns the value 4. So what are we left with? $a == 4 But what is $a at this point? Well, it is 4 of course, because we just set it. So we have: 4 == 4 If you can find a language where this expression doesn't return true, regardless of the initial value of $a, then you should file a bug against that language. ------------------------------------------------------------------------ [2012-02-26 17:54:18] antickon at gmail dot com Description: ------------ An assignment expression can change the order of operation for == and != (and possibly other binops) Test script: --------------- <?php $a = 3; var_dump( $a == ( $a = 4 ) ); Expected result: ---------------- bool(false) evaluation of $a == ( $a = 4 ) should be as follows: left side of the comparison is evaluated (evaluates to 3) right side of the comparison is evaluated (4 is assigned to $a, evaluates to 4) 3 == 4 finally evaluates to false Actual result: -------------- bool(true) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=61188&edit=1