php中的post增量和pre increment简单方程

Question

I have this equation:

<?php
$i=5;
$i += $i++ + ++$i;
echo $i;

It gives output 19. Which strange to me as I am new in php. According to my effort I see how it deal.

first ++$i = 5 + 1 = 6 then

$i++ = 6 then

$i + = 6 + 1 = 7 and in total its,

$i += $i++ + ++ $i equals to 7+6+6=19.

can any one tell the how $i += 6 + 1 = 7

Sorry for my bad english. Thanks in advance.

Answer 1

$i=5; 
$i += $i++ + ++$i;  => $i = 5($i++) + 7(++$i) +7($i); echo $i(19);

    =>$i += $i++  +  ++$i;
    => 7  = 5 +7 ;

first it run from right side .first i value will remain 5 then is post increment and becomes 6 and when you add ++$i it will become 7 due to pre increment. and at the last i value will be added which already becomes 7