<style>
    img.image{
        max-width:200px;
        max-height:200px;
        padding:10px;
    }
</style>
<?php
    $dir = scandir("images/");
    $i = 0;
    foreach($dir as $key => $file){
        echo "<a href='images/{$file}'><img src='images/{$file}' class="image" /></a>";
        $i++;
        if($i%3==0){
            echo "<br />";
        }
    }
?>