PHP Array-Copy and For-Loop - whats wrong?-CodePudding

My goal is, to create a web based gallery.

To achieve this, i'm reading out a directory, store the file-names within an array and returning the array back, to load the images. This works.

But, the images are not sorted, or, to be precise, the images are sorted in a non intuitive way. This way works:

  $allFiles = array();
  $count = 0;
  if (is_dir($thumbnail_dir)) {
    if ($dh = opendir($thumbnail_dir)) {
      // Read files
      while (($file = readdir($dh)) !== false) {
        if($file != '' && $file != '.' && $file != '..') {
          $allFiles[$count] = $file;
          $count  ;
        }
      }
      $count--;
    }
  }
  echo json_encode($allFiles);

If i return this to my JavaScript, it works, but the images are not really sorted. To get the the images sorted, in a way, I define, I add this, and it works too.

  sort($allFiles);
  echo json_encode($allFiles);

But, beacuse I have to many images, to load all at once, I added a loop, to select a chunk of file an return only this chunk. I want to load initially 20 images on my page, so the first call will be $firstIndex = 0 and $lastIndex = 20; the second call will be $firstIndex = 20 and $lastIndex = 40; and so on. Without chunking, it works perfect. But with chunking, it chrashs.

  for ($i = $firstIndex; i < $lastIndex; $i  ) {
    $j = $i - $firstIndex;
    $fileNames[$j] = $allFiles[$i];
  }
  echo json_encode($fileNames);

At this point must be occur an error and nothing appears on my page.

What do I wrong?

Greets Johannes

CodePudding user response：

I think you missed a $ sign for i at i < $lastIndex

for ($i = $firstIndex; $i < $lastIndex; $i  ) {
    $j = $i - $firstIndex;
    $fileNames[$j] = $allFiles[$i];
  }
  echo json_encode($fileNames);