Subtracting 1 from a value and storing it in another variable

Question

I vaguely remember running into this problem before, but I'm wondering if this just doesn't work in PHP:

echo $counter; // outputs 4
$output = $counter--;
echo $output; // outputs 4

If I do something like:

$output = $counter - 1;

I have no problems whatsoever.

Can someone shed some light on this?

Thanks, Ryan

Answer 1

What you want is the pre-decrement operator:

echo $counter; // outputs 4
$output = --$counter;
echo $output; // outputs 3

Answer 2

Your code, using post-decrement, should be read as:

• set the value of $counter to $output; then
• decrement $counter

What you want is the following (pre-decrement), which says

• decrement $counter; then
• set the value of $counter to $output

The code is:

<?php
  $counter = 4;
  echo $counter;
  $output = --$counter;
  echo $output;
?>