gallery with next and prev function - php

Question

I'm working on an image gallery as my first real project as of learning php.. The problem I'm not able to get around somehow is using the "previous" button. My "next" function grabs the next 6 images from the folder and posts them to the page, my prev function does this in reverse.. but that's incorrect, can you help? oh, and this code is sloppy beginner code so i'm happy for tips :)
<?php
session_start();
if(session_id() == '') {
$_SESSION["count"] = 0;
}
function PostHTML($id, $file) {
if($id==0) {
echo "<div class=\"item\"><div class=\"well\"><img
class=\"img-responsive\" src=\"$file\" alt=\"\"><p>blahblahblah xxxxxx</p></div></div>";
}else{
echo "<div class=\"item\"><div class=\"well\"><video autoplay
loop class=\"img-responsive\"><source src=\"$file\" type=\"video/mp4\"></video></div></div>";
}
}
function next_img() {
$dir = "images/src/*.*";
$files = array();
$start = $_SESSION["count"];
$end = $_SESSION["count"]+6;
$y=0;
foreach(glob($dir) as $file) {
$files[$y] = $file;
$y++;
}
for($i=$start; $i < $end; $i++){
if(pathinfo($files[$i], PATHINFO_EXTENSION)=="jpg") {
PostHTML(0,$files[$i]);
} else {
PostHTML(1,$files[$i]); }
}
$_SESSION["count"]+=6;
}
function prev_img() {
$dir = "images/src/*.*";
$files = array();
$start = $_SESSION["count"]-1;
$end = $_SESSION["count"]-6;
$y=0;
foreach(glob($dir) as $file) {
$files[$y] = $file; //100 files
$y++;
}
for ($i = $start; $i > $end; $i--) {
if(pathinfo($files[$i], PATHINFO_EXTENSION)=="jpg") {
PostHTML(0,$files[$i]);
} else {
PostHTML(1,$files[$i]);
}
}
$_SESSION["count"]-=6;
}
?>

Answer 1

If i were to do something like this I might create a File Controller class to manage all the file operations i might need.
<?php
class FileController
{
private $_dir = "DIR";
private $files;
private $current;
function__construct()
{
$current = 0;
$files = scandir($_dir); // scans the dir to get a list of file names
if(!$files) echo "Failed To Load Files"; // failed to load files
else
{
$this->file = $files; // objects propery contains all file names in array;
}
}
function PostHTML($fileName) {
$src = $this->_dir + "/" + $fileName;
if(!$fileName)
{
return "<div class=\"item\"><div class=\"well\"><img
class=\"img-responsive\" src=\"$src\" alt=\"\"><p>blahblahblah xxxxxx</p></div></div>";
}
else
{
return "<div class=\"item\"><div class=\"well\"><video autoplay
loop class=\"img-responsive\"><source src=\"$src\" type=\"video/mp4\"></video></div></div>";
}
}
function nextImg()
{
$current = $this->getCurrent();
$end = $current + 6;
$this->setCurrent($end);
$files = $this->files;
$html = "";
for($i = $current; $i<= $end; $i++)
{
$html += postHtml($files[$i]);
}
echo $html;
}
function prevImg()
{
$current = $this->getCurrent();
$end = $current - 6;
$this->setCurrent($end);
$files = $this->files;
$html = "";
for($i = $current; $i>= $end; $i--)
{
$html += postHtml($files[$i]);
}
echo $html;
}
function getCurrent()
{
return $_SESSION['current'];
}
function setCurrent($current)
{
$_SESSION['current'] = $current;
}
}
?>