Inserte data into table when click on button

Inserte data into table when click on button

I know how to insert data into table and its working perfect, but I want
to know how can I insert data into table just when user click on button
called "ADD" this is a few lines of my code
"; mysql_query ("INSERT INTO list
(student,school,major)VALUES('$student','$school','$major)"); ?>
I want the data add to the table only when user click on ADD button...
THANK YOU!