<?php
$thumb = "thumb"; //thumb folder name whit no "/" 
$images = "img"; //images folder name whit no "/"


$listOfFilesToSort = array();
$folder = opendir($images);
while ( false !== ( $file = readdir( $folder ))){
if ( $file != "." && $file != ".." )
$listOfFilesToSort[$file] = $file;	
}
sort( $listOfFilesToSort );
foreach ( $listOfFilesToSort as $file )
{
echo '<a href="'.$images.'/'.$file.'"><img src="'.$thumb.'/'.$file.'" class="gal"></a>';
}
?>

Gallery from folder whit php

php

PHP