Test it:

one two three four five

HTML

<form action="<?=$_SERVER['PHP_SELF']?>" method="post">
<select name="test[]" multiple="multiple">
	<option value="one">one</option>
	<option value="two">two</option>
	<option value="three">three</option>
	<option value="four">four</option>
	<option value="five">five</option>
</select>
<input type="submit" value="Send" />
</form>

PHP

<?php
	$test=$_POST['test'];
	if ($test){
	 foreach ($test as $t){echo 'You selected ',$t,'<br />';}
	}
?>