a = (a + b) - (b = a); C++ vs php

Question

I\'ve been looking around and found formula: a = (a + b) - (b = a) it is supposed to swap two variables (or objects in some cases). However I tested it with C++

Answer 1

For PHP:

$a = 10;
$b = 20;
$a = ($a + $b) - ($b = $a);
//executes like thus
$a = (30) - ($b = $a);
$a = (30) - ($b = $a = 10); //new $a still not computed, using older $a
$a = (30) - (10);
$a = 20;
//then, $a=20 and $b = 10

This is totally related to Operator Precedence, this might be same in C or might not, it depends on precedence if unexpected behavior not occur.