检查所选选项是否唯一

Question

I'm working on school project and I have a problem with validating select boxes. It's very simple trip planner and let's say that I have 3 places that user visited and now he has the option to determine the order of visits. For example: [1]cinema, [3]concert,[2]shopping mall. The select boxes are generated automatically by PHP. How can I write universal jQuery script that validates the select boxes that each of them is unique?

Here is PHP code that generates the select fields;

    $title = $_GET['title'];
    $elements = count($_GET['eventid']);
    echo "<h5>Order your trip</h5>";
    foreach($_GET['eventid'] as $index => $id)
        {
        echo"<strong>" .$title[$index] . "</strong><select name='".$id."'>";
            for($i=1;$i<=$elements;$i++){
                echo"<option value='". $i ."'>". $i ."</option>";
            }
        echo"</select><br><br>";
        }

Now I would like to validate select boxes no matter how many events there are. I came up with this code. It works but can it be done easier?

    $('#validate').click(function() {
    var selectValues = new Array();
    $('select.order').each(function() {
        selectValues.push($(this).val());
    });
    var elements = selectValues.length;
    var i;
    for (i = 0; i < elements - 1; i++) {
        if (selectValues[i] == selectValues[i + 1]) {
            alert('error');
        }
    }
});