Dealing with infinite loops - php

Question

I'm trying to learn PHP programming through trial, error and lots and lots of practice.
I've been working on a directory bases image gallery for the last few days and it seems to work fine. I can upload pictures and create new albums. Plus whenever I see a full size picture I have links to the previous and next pictures in the directory.
Now this is where I ran into problems. Once you got to the end of the directory the code would start an infinite loop while it searches for the next file, which isn't there.
So I altered my code and it now looks something like this:
$x = 1;
$dir = opendir($base.'/'.$get_album);
while ((($file = readdir($dir)) !== FALSE) && ($x == 1)) {
while ($img < $file) {
$img++;
$image_exists = file_exists($base.'/'.$get_album.'/'.$img);
if ($image_exists) {
echo "<a href='member.php?album=$get_album&imgID=$img'>
<img src='$base/$get_album/$img' width='70' align='right'>
</a>";
break;
}
$x++;
}
}
This works when I get to the last picture in the directory. So I thought I'd do the same for when I get to the first picture and just invert the operators like so:
$x = 1;
$dir = opendir($base.'/'.$get_album);
while ((($file = readdir($dir)) !== FALSE) && ($x == 1)) {
while ($img > $file) {
$img--;
$image_exists = file_exists($base.'/'.$get_album.'/'.$img);
if ($image_exists) {
echo "<a href='member.php?album=$get_album&imgID=$img'>
<img src='$base/$get_album/$img' width='70' align='right'>
</a>";
break;
}
$x++;
}
}
This however DOES NOT work. I can't understand why that would be the case and I've tried to change things around a few dozen times but I cant seem to make it stop looping.
What am I doing wrong?
Thanks in advance for your help (and for reading through all this).

Answer 1

The issue could likely be related to the fact that readdir returns a string, and you are treating it as if you know its a number. You might find that it is returning you something at the start or end, such as the parent directory '..' as a string or the current directory as a string '.'.
If you want to iterate over the directories, you should check that the return value from readdir is not '.' or '..' specifically.

Answer 2

Please use a better format to your code (it's really painful read it), for instance, in netbeans you can use shiftalt F to format automatically.
I want address your attention to this line:
$image_exists= file_exists($base.'/'.$get_album.'/'.$img);
That is a possible source of errors. If only $base.'/'.$get_album.'/' exists then:
$image_exists= file_exists($base.'/'.$get_album.'/'.$img); // is true even if $img is empty!!!
But moreover:
What is $img? You treat it as a number when do $img++ and then as a string. That is not good for your health.
A good start it should be initialize your vars at the beginning of your code. And then use them in consonance.

Answer 3

I think there is something fundamentally wrong with the design, you are comparing $img, an uninitialized integer, to $file, a string.
It also seems needlessly complicated, as you are reading files from a directory, then check if they exist and break out of your loop if they do.
Perhaps with a clear view of the directory structure and what you are trying to do, I could provide a more detailed answer, but I think you need to go back to the drawing board.