Program Flow Control

Worker Joined: Feb 18, 2004 Posts: 244

Hi,

I'm developing a php module for my nuke site and I'd like to ask a question about flow control.

At the end of many functions within nuke you see things like this:

Code:

header("Location: admin.php?op=addStudent&msg=$msg");

From my C backbround I can tell this is a type of branch. Your code continues execution with the supplied function and arguments.

However this is not absolute. It cought me off guard today when these lines were totally ignored and program execution continued to flow through my if statements.

Here's my sample:

Code:

function insertStudent($name, $nukeid, $cid, $status){


   global $prefix, $db;





   $name=filter_text($name, "nohtml");


   $nukeid=intval($nukeid);  // Make sure it's an intiger


   


   $username = isSiteMember($nukeid);


   


   if($username == NULL) { 


      $msg = _STUDENT_NOTFOUND;  // Nuke id does not exist


      header("Location: admin.php?op=addStudent&msg=$msg");


   }


   


   $sid = isStudent($nukeid);


   if ($sid) { 


      $msg = _STUDENT_ALREADY_IN; // Student is already in university - cant add again


      header("Location: admin.php?op=addStudent&msg=$msg");


   }





   if ($name!="") {


      $username=$name;


   } 


   


   $insert = $db->sql_query("INSERT INTO ".$prefix."_university_students VALUES (NULL, '$nukeid', '$username', '$status')");


}

In this bit of code I first expected program execution to skip the sql insertion if certain conditions were met, however that is not the case.

Even when the if statement pulls you in you still don't branch immediately. The sql insert is still done, even though I did not want it. Sad

Do I have a syntax error, or is this not the way to control a programs flow?

Thanks,
Darrell

Site Admin/Owner Joined: Aug 27, 2002 Posts: 17088

Kinda-sorta. It actually writes an HTTP header and as such, no code can be written to the browser before it or you will receive the 'headers already sent' message unless output_buffering is on.

I'm not sure exactly where your code fails, but I would rewrite this statement

Code:

if($username == NULL) {

as

Code:

if (isnull($username)) {

Posted: Wed Feb 18, 2004 3:52 pm

Oh, and it is a good idea to add die(); after those header statements Smile

Code:

header("Location: admin.php?op=addStudent&msg=$msg");


die();

Posted: Wed Feb 18, 2004 4:01 pm

Thanks for the tip, I rewrote it to if (is_null($username)).

I've been trying to figure this out now for over 7 hours. Something isent right with this, or with my understanding of it.

The code isent exactly failing. I use the two if statements to return an error message to the addStudent function so that the user can give it antoher shot.

They are both actually working. I've put echo statements on every single line and watched my data as I step thru it. I'm droping into the if statements and upon exit of this function I'm going to the appropriate spot..

The problem is that the insert command runs no matter what I do.

If I'm error trapping I don't want the insert command to run on bad data. What am I missing?

I don't believe those header statements are right...

Posted: Wed Feb 18, 2004 4:03 pm

OMG,

That fixed it!

Thanks... What a waste of a day...... geessss.

Posted: Wed Feb 18, 2004 4:11 pm

I thought that litlle nuance might just do it Wink