Explain does running `$i = 1; $i += ++$i + ++$i;` set $i to 8?

[gokberx]

\[code\]<?$i = 1;$i += ++$i + ++$i;echo $i;?>\[/code\]Output is 8. However, I think it should be 6. I interpret the line:\[code\]$i += ++$i + ++$i;\[/code\]as \[code\]1 += ++1 + ++2 i.e 1 += 2 + 3 i.e 1 += 5i.e 6\[/code\]However the output you get is 8. Can someone explain why?