deleting a file from the data base by clint - php

Question

function appoint_del(sat,sat1)
{
if(confirm("Are You Sure To delete Selected Person Details Completely?"))
{
document.form1.action="student.php?cedit="+sat+"&did="+sat1;//
document.form1.submit();//an alternative to call form
}
}
<?
if($_GET['did']!="")
{
$del=executeupdate("delete from table2 where id=".$_GET[did]);
redirect("student.php?succ=3");
}
?>
To delete the content in data base by clint I have successfully did the job but I am not completelly aware of what is happining by the statement1 document.form1.action="student.php?cedit="+st+"&did="+st1;
and statement2
document.form1.submit()
can any one explane it?
and can sugest any good reference book for clarifing these type of doubts?

Answer 1

document.form1.action="student.php?cedit="+sat+"&did="+sat1;
This line of JavaScript sets a html form's action to the student.php page and appends the two parameters "cedit" and "did" along with their values. I assume you have a form on your page somewhere.
document.form1.submit();
This submits that form. I don't know where to or by what method (POST, GET) because you haven't provided any details on the form. I assume it submits back to the same page because the next line is a handler:
if($_GET['did']!="")
This detects whether the form was submitted by checking if the "did" parameter is present.
$del=executeupdate("delete from table2 where id=".$_GET[did]);
This seems to execute a database query with a massive SQL injection vulnerability. Very dangerous.
redirect("student.php?succ=3");
Redirects back to the same page again, this time passing in a different "succ" parameter which I assume is handled via some other code that you haven't provided.