Código PHP:
if (isset($_POST['hola']))
echo $_POST['hola'];
Código HTML:
<form action="prova.php" method="post" name='asdf'> <select name="hola" size="5" multiple> <option value="qqqqqq"> qqqqqq</option> <option value="wwwwwwwwww"> wwwwwwwwww</option> <option value="eeeeeeeee"> eeeeeeeee</option> <option value="rrrrrrrrrrr"> rrrrrrrrrrr</option> <option value="ttttttt"> ttttttt</option> <option value="yyyyyyyyy"> yyyyyyyyy</option> <option value="uuuuuuuu"> uuuuuuuu</option> <option value="iiiiiiiiiiii"> iiiiiiiiiiii</option> <input type="submit" value="enviar" /> </select> </form>