如果在第一个下拉列表中选择了一个值（使用变量），则显示第二个下拉列表？

Question

Is there any way I can select a certain value in a dropdown list and according to that selection display a second dropdown list? I know how to do it with just normal words, but what if I use variable names?

University Name: <select name="university" id="university">
<?php 
    while($row = mysql_fetch_array($uniName)) {
        echo "<option>" . $row['uni_name'] . "</option>"; 
    }
?> 
</select>
<br/>
Course Name: <select name='course' id='course'>
<?php 
    while($row = mysql_fetch_array($courseNames)) {
        echo "<option>" . $row['course_name'] . "</option>"; 
    }
?>
</select>

So as you can see, in the first dropdown list I've added all the retrieved university names from my database. I did the same for the courses as well.

Now how can I modify the code below:

$(document).ready(function() {
    $('#course').hide();

    $('#university').change(function () {
        if ($('#university option:selected').text() == "Harvard University"){
            $('#course').fadeIn('slow');
        }
        else { 
            $('#course').fadeOut('slow');
        }
    });
});

Instead of "Harvard University", I want to put a variable there according to what the user has selected. Something like $university_name and then I'll create a new query and display only the courses belong to a certain $university_name.

Answer 1

As already stated in my comments, I recommend using AJAX to fill the course box.

$.ajax("getCourses.php", {
    data: { UID: uid },
    type: 'POST',
    done: function(result) {
        $("#course").html(result);
});

This will fill the select tags with whatever getCourses has for output.

UID would of course be the ID of the university in question.

This page has all the info you need. For further information and examples, Google is your friend :)