error in gallery pagination - php

Question

I've adapted a simple paginated gallery to my needs, but it doesn't work as expected: usually it puts well the first "page" og pictures then in some cases it just skip some pictures and then go to further ones, in other cases it just do not load any other page (I'm using infinitescroll)
here is the php function:
function makeGallery($path, $directory, $seo){
$dir = $path . "/" . $directory;
$handle = opendir($dir);
while ($file = readdir($handle)){
if($file == '.' OR $file == '..' or $file == 'thumbs' or $file == '.DS_Store')
continue;
else
$result_array[]=$file;
}
$filecount = count(glob("" . $dir . "*.jpg"));
closedir($handle);
array_multisort($result_array, SORT_ASC);
$rows = 3;
$cols = 8;
if(isset($_GET['page'])){
$page = $_GET['page'];
}else{
$page = 0;
}
$num_pics = count($result_array);
$cells = $rows * $cols;
$pages = ceil($num_pics / $cells);
$num_pages = $pages - 1;
$output = array();
$slices = array();
$push = 0;
$showpage = $page + 1;
for($k=0;$k<$pages;$k++){
array_push($slices, $push);
$push = $push + $cells;
}
for($k=0;$k<$pages;$k++){
if($page == key($slices)){
$output = array_slice($result_array, current($slices), $cells);
}
next($slices);
}
reset($output);
print '<div class="container-fluid">
<div class="row">';
print "<ul id='photoswipe' class='thumbnails'>";
for($i=0;$i<$rows;$i++){
for($j=0;$j<$cols;$j++){
if(current($output) != false){
$value = current($output);
$parts = Explode('.', $value);
$title = $parts[count($parts) - 2];
$parts = Explode('-', $title);
$title = $parts[1];
if ($title == "") $title = $value;
print "<li class='box'><a title='$title' rel='group' class='thumbnails' href='$dir/$value'><img width='$width' height='inherrit' src='$dir/thumbs/$seo-$value' /></a></li>";
next($output);
}else{
print "</ul>";
}
}
}
$ref = $_SERVER['PHP_SELF'];
if($num_pages == '0'){
print " ";
print " ";
}elseif(($page == '0')||($page == '')){
$next = $page + 1;
print " ";
print "<a id='next' href='$ref?page=$next'> </a>";
}elseif($page == $num_pages){
$prev = $page - 1;
print "<a id='prev' href='$ref?page=$prev'> </a>";
print " ";
}else{
$next = $page + 1;
$prev = $page - 1;
print "<a id='prev' href='$ref?page=$prev'> </a>";
print "<a id='next' href='$ref?page=$next'> </a>";
}
echo "<nav id='page-nav'>
<a href='$ref?page=$next'></a>
</nav></div></div>";
}
I'm sure there should be some silly bug that i've not spotted and i hope that some experienced php programmer can find it very easily.
you could see the gallery (and its problem) on http://eikonabox.com/page/portrait.php
(in the portrait gallery as you can see it jumps from the number 24 directly to number 49)
Thank you all

Answer 1

If somone get stuck in this kind of problem I've resolved this way:
function makeGallery($path, $directory, $seo){
$dir = $path . "/" . $directory;
$filearray = array();
if ($fil = opendir($dir)) {
while (($file = readdir($fil)) !== false) {
if ($file != "." && $file != ".." && $file != "thumbs" && $file != ".DS_Store") {
$filearray[] = $file;
$page = empty($_GET['page']) ? 1 : $_GET['page'];
$num_per_page = 25;
$total_pages = ceil(count($filearray)/$num_per_page);
}
}
array_multisort($filearray, SORT_ASC);
print '<div class="container-fluid">
<div class="row">';
print "<ul id='photoswipe' class='thumbnails'>";
for($i = ($page - 1) * $num_per_page; $i < $page * $num_per_page; $i++){
$value = basename($filearray[$i]);
$parts = Explode('.', $value);
$title = $parts[count($parts) - 2];
$parts = Explode('-', $title);
$title = $parts[1];
if ($title == "") $title = $value;
if($value != "")
print "<li class='box'><a title='$title' rel='group' class='thumbnails' href='$dir/$value'><img width='$width' height='inherrit' src='$dir/thumbs/$seo-$value' /></a></li>";
}
closedir($fil);
}
print "</ul>";
$ref = $_SERVER['PHP_SELF'];
if($num_pages == '0'){
print " ";
print " ";
}elseif(($page == '0')||($page == '')){
$next = $page + 1;
print " ";
print "<a id='next' href='$ref?page=$next'> </a>";
}elseif($page == $num_pages){
$prev = $page - 1;
print "<a id='prev' href='$ref?page=$prev'> </a>";
print " ";
}else{
$next = $page + 1;
$prev = $page - 1;
print "<a id='prev' href='$ref?page=$prev'> </a>";
print "<a id='next' href='$ref?page=$next'> </a>";
}
echo "<nav id='page-nav'>
<a href='$ref?page=$next'></a>
</nav></div></div>";
}