how to show random pictures using php?

[Swiebertjeee]

I want to show 4 random pictures from a folder (there are a total of 7 pictures) but I'm not sure how to do this. 

 

I know if I have only 1 I can simply use this code : 

<?php 	$total = "10"; 	$file_type = ".jpg"; 	$image_folder = "img/random"; 	$start = "1"; 	$random = mt_rand($start, $total); 	$image_name = $random . $file_type; 	echo "<img class=\"random\" src=\"$image_folder/$image_name\" alt=\"random\" />"; ?>

or put them into an array and do the same thing. 

 

But in that case I will get the possibility for the same images shown. 

[mantylt]

Create new array $used_values and every time you select new value ($random) check if $random doesn't already exists inside $used_values. If it does, pick new $random and continue when it doesn't.