获取下拉列表的值并在php中使用它

Question

I have designed a form in html5 with 4 dropdowns 1-Year 2-Department 3-Semester 4-Subject

I have used php to get the values of year,department,and semester.Now what i want is that based on the user selection for year,department,semester i want to get the subjects dynamically

I have written a query to get the subjects based on year,department,and semester

Query //for subject dropdown

select s.sub_name from 
subject s
inner join year y
on s.year_id=y.year_id
inner join dept d
on s.dept_id=d.dept_id
inner join sem sm
on s.sem_id=sm.sem_id
where y.year_id='' and  // get selected value from dropdown
d.dept_id='' and // get selected value from dropdown
sm.sem_id=''// get selected value from dropdown

Now how will i send those selected drop down values to the query in php dynamically.

Answer 1

I suppose your dropdowns use <select> with multiple <option> tags (see W3schools). Give your select a sensible name, and the value of the dropdown will be in $_POST['selectName'] or $_GET['selectName'] (depending on your form submission method).

If you want to do this dynamically (i.e. when a user changes the dropdown), you'll have to come up with some JavaScript (AJAX) posting the selected value to your php-page (e.g. using jquery.post). You can then use the result of that post-call to fill in your dropdowns.