Try this, this will fulfill your requirement
Code:
<?php
$my_folder = "my_images";
$files = array();
if ($handle = opendir($my_folder))
{
while (false !== ($file = readdir($handle)))
{
if ($file != "." && $file != "..")
array_push($files,$file);
}
closedir($handle);
}
if ( isset($_GET['id']) )
$id = $_GET['id'];
else
$id = 0;
?>
<img src="<?=$my_folder."/".$files[$id];?>" alt="" /><br />
<?php
if ($id > 0)
echo "<p style=\"width:200px; float:left;\"><a href=\"".$_SERVER['PHP_SELF']."?id=".($id-1)."\">Previous</a></p>";
else
echo "<p style=\"width:200px; float:left;\">Previous</p>";
if ($id <= count($files) - 2)
echo "<p style=\"float:left;\"><a href=\"".$_SERVER['PHP_SELF']."?id=".($id+1)."\">Next</a></p>";
else
echo "<p style=\"float:left;\">Next</p>";
?>