CODEWITHSUNDEEP
php
Eran Machiels
Eran Machiels

Reputation: 881

Difference $i++ and ++$i when 0

I came along this script lately: 

$i = 0;
$x = $i++; $y = ++$i;
print $x; print $y;

The output was 02. I can imagine that you can't count +1 on $i with ++ while it is 0, but why does $y output as 2? And why isn't the output 11 or 01?

Upvotes: 1

Views: 191

Answers (1)

Jonathan Kuhn
Jonathan Kuhn

Reputation: 15301

post increment vs pre increment.

Post: Trailing $i++ means that $i is returned and then incremented after.

Pre: Preceding ++$i means that $i is incremented and that result is returned.

So $x is set to 0 (the initial value of $i) and then incremented. $i is now equal to 1. Then $i is incremented again to 2 and that value is set in $y. So in the end, $x=0 and $y=2 and $i=2. Your code could be rewritten as:

$i=0;
//x, post increment, set x to i then increment after.
$x=$i;
$i=$i+1;

//y, pre increment, increment first and then set y to i.
$i=$i+1;
$y=$i;

Same thing applies to the decrement operator --$i and $i--.

Upvotes: 2

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