I'm looking to validate whether or not a user selects an option from a drop down menu:

PHP Code:
<select name="state[]">
option value="NULL">-- Please select a state --</option>
option value="AK">AK Alaska</option>
option value="AL">AL Alabama</option>
option value="WY">WY Wyoming</option>
How do I check if they leave the default state selected? I really am having a hard time with how PHP interprets selected options (Please no Javascript.)