Question about while loop

[dimkasmir]

Hi,
I'm really new at PHP and have a simple question about the while loop.
I am trying to program a script and at the end I have this loop:

while (($W<>$D) && ($X<=100000) && ($D<>0))
{
		$X++;
}

echo $D;
echo $W;

This gives me 0 and 0 which shouldn't happen becaused of $D<>0. Maybe there's something wrong wiht my syntax?
The relations between W, D and X are coded before that but that shouldn't be signigicant to the answer to my question.
Thanks a lot!

[Kudose]

$D must equal 0 or $D equals $W.

<?php
  $W = 1;
  $D = 2;
  while (($W<>$D) && ($X<=100000) && ($D<>0))
  {
  $X++;
  }
  echo $D;
  echo '<br />';
  echo $W;
?>

Works just fine.

[laserlight]

I think you misunderstood what a loop condition means. A loop runs while its condition is true, so after the loop has ended, the variables involved in the loop must be in a state such that the loop condition is false. Consider:

while ($x <> 0)
{
    $x++;
}
echo $x;

Suppose the value of $x was a non-positive integer before the loop. What is the value of $x after the loop? The answer must be 0, since only when $x = 0 then ($x <> 0) is false.

Of course, in your example there are other variables at play, so the loop condition is more complex hence we cannot say if the value of $D necesarily is 0 after the loop, but we can say that at least one of these conditions is true:
1. The value of $W is equal to the value of $D
2. The value of $X is greater than 100000
3. The value of $D is equal to 0

Incidentally, I suggest using != instead of <> as it seems more common in PHP code.