Iterate over all custom fields - Wordpress tutorial

<?php
$custom_fields = get_post_custom($post->ID);
$my_custom_field = $custom_fields['my_custom_field'];
foreach ( $my_custom_field as $key => $value ) {
    if ($key == ‘Level’){
        switch ($value){
            case ‘Easy’:
                echo “<img src=‘easy.gif’>”;
                break;
            case ‘Difficult’:
                echo “<img src=‘difficult.gif’>”;
                break;
        }
    }
    else{
        echo $key . “: " . $value . "<br />";
    }
?>