Addition precedence post increment bug.

bug.php

<?php
$a = 0; echo $a+$a+$a++; //0
$a = 1; echo $a+$a+$a++; //3
$a = 2; echo $a+$a+$a++; //6
$a = 3; echo $a+$a+$a++; //9

echo PHP_EOL;

$a = 0; echo $a+$a++; //1 <-- should be 0
$a = 1; echo $a+$a++; //3 <-- should be 2
$a = 2; echo $a+$a++; //5 <-- should be 4
$a = 3; echo $a+$a++; //7 <-- should be 6

echo PHP_EOL;

$a = 0; echo $a++; //0
$a = 1; echo $a++; //1
$a = 2; echo $a++; //2
$a = 3; echo $a++; //3

/*
0369
1357
0123
*/

/*
Which cause confusion for people who do..
echo $a+$a++;    //3
echo $a+$a+$a++; //3

And ask themselves why:
https://stackoverflow.com/questions/47766470/why-these-both-post-increment-in-php-gives-the-same-answer
https://stackoverflow.com/questions/22314442/php-operator-precedence-undefined-order-of-evaluation
*/