How to use SELECT with multiple options enabled in forms....

Now, use SELECT is simple enough. The Select Name gives a value, the one you selected of course... However, I yet have to find a way to actually determine how I could fetch i.e. the results from a SELECT multiple-choice menu. What if I want the website visitor to choose from multiple values, and read them in a PHP script after the form is submitted? Suggestions or ideas of how to solve this? I figured this is probably a very easy task, but I've done a couple attempts, and yet unsuccessful... I can make and read the values of multiple checkboxes, but I cant figure out how to do this with a select .... Best regards, Robert.