header ("Location: ...... headers already sent error

ejwf

Having a problem with 'Warning: Cannot modify header information - headers already sent'

I have checked the search facility on these boards and found out what the problem is, have amended it as much as I can, but still cannot get the code to work.

Brief outline of what I am trying to do - user logs in on login page - this form directs to page authority.php (the code with the error), based on the login name I check in the database to see what password authority level they have been assigned and based on this level 1-4 I send them to the appropriate page......

code for page authority.php

session_start();
$_SESSION['username'] = $username;
require_once ('../mysql_connect.php');
$query = "SELECT `AuthorityLevel` FROM `tblUser` WHERE `CLogIn` = '$username'"; 
$result = mysql_query($query) 
   or die(mysql_error());
$row = mysql_fetch_array($result); 
$AuthorityLevel = $row["AuthorityLevel"]; 
if ($AuthorityLevel = 1){header("Location: level1.php");}
elseif ($AuthorityLevel = 2){header("Location: level2.php");}
elseif ($AuthorityLevel = 3){header("Location: level3.php");}
else{header("Location: level4.php");}

I have taken out all the blank space I can find - there is no blank space prior to <?php tag - this is why the code looks so cramped, I took out all the space just to be safe!
The error message give the line where the output started as the line require_once ('../mysql_connect.php');

but I have to be connect to the database to query it and get the results to do the if / else bit of code.

Again, searching these boards, I have seen codes suggested that look similar so I really don't know where i am going wrong......how else I can achieve this........

any ideas will be gratefully received.

Weedpacket

You seem to be awfully confused. About the difference between PHP and HTML, for example. And about what the other threads were saying.

One
So as soon as you output any content - HTML, image file, even a single blank line - PHP takes all the headers it has collected so far, fires them off, and then starts sending that content. Once that's happened it's too late to send any other headers with that response. If you try you get the error message this post is about.

Two
Yeah, you can't send ANY output before a header() call. Not print(), not echo(), no HTML, no whitespace.

And read the manual, its covered there too: www.php.net/header

Three
"<HTML>
<HEAD>
<TITLE>Public Information and Library Resources Board</TITLE>
</HEAD>

<BODY>"

That is an example of output before the header()

Four
Read the PHP Manual on header()
quote:Remember that header() must be called before any actual output is sent, either by normal HTML tags, blank lines in a file, or from PHP. It is a very common error to read code with include(), or require(), functions, or another file access function, and have spaces or empty lines that are output before header() is called. The same problem exists when using a single PHP/HTML file.[/quote]
So the problem isn't caused by space characters in your PHP code.

If you read the error message, it will tell you where the offending output is located: it's the lines where PHP reported that the headers were sent at.

PS:
if ($AuthorityLevel = 1){header("Location: level1.php");}
should be
if ($AuthorityLevel == 1){header("Location: level1.php");}

ejwf

Yes confused is a very good way of putting it.........

OK, so if I cannot use header ("Location: ......"); to forward to another page - depending on the results of a query - then what can I use?

I've read the manual section on header () and I understand why I cannot use it in this instance, I understand that my code is WRONG and why, but what can I use instead of header ()?

Weedpacket

It's impossible to say because of the amount of information you've left out of your post. You don't even give the full error message or say what exists on the lines it refers to (if you read the error message, it will tell you where the offending output is located: it's the lines where PHP reported that the headers were sent at). The database query is irrelevant. What is relevant is what output your script is producing before it is sending the headers (as implied by the error message).

Drakla

Just in case, have you made sure that there's no space, returns etc before the opening tag in your mysql_connect.php script, and that it outputs absolutely nothing.

I'll shut up, I'm tired.

ejwf

absolutely positive - no space, nothing before the <?php tag.
The only thing on this page is the code, no html, nothing.

Weedpacket

So what's the full error message?

ejwf

The full error message is......
Warning: Cannot modify header information - headers already sent by (output started at ///mysql_connect.php:20) in /**//authority.php on line 10

line 10 is
if ($AuthorityLevel = 1){header("Location: level1.php");}

another development - could this have anything to do with sessions timing out or something, because I have logged in and tried it, the code worked OK, but when I tried it again with a different username it came up with the error message.......

RHolm

Originally posted by ejwf

Warning: Cannot modify header information - headers already sent by (output started at ///mysql_connect.php:20) in /**//authority.php on line 10

what's on line 20 of mysql_connect.php? that's where the error is.

crookedgoomba

require_once ('../mysql_connect.php');

does mysql_connect.php have any output?? that is where the headers are that are being outputted. supposedly...

ejwf

Replying to both questions;

there is no line 20. the code is 15 lines long, and there is nothing after the ?> tag, no returns, no spaces. That is it on the page.
not sure what you mean about outputting anything off mysql_connect.php. in the page authority.php all I am doing is calling in this file to connect to the database. in the file mysql_connect.php just contains all the information (host, password, user, database) to connect to the database. Checked on this file also, no blank space prior to the <?php tag.

has anyone got any thoughts on the session side of the problem? could this be where I have gone wrong?

Weedpacket

Really? PHP is reporting an error on line 20 of a file that is only 15 lines long? We are talking about '../mysql_connect.php' here?

ejwf

I really don;t know what is going on with my code.
So I have stripped it all out and started again.
I have created new versions of both authority.php and mysql_connect.php and it now seems to work.
Nothing to do with sessions (I don't think) so the only thing I can assume is that there was some blank space after the ?> end tag on mysql-connect.php. would this have caused the problem?
thanks for all your patience, as I say, I think this has solved the problem...........

Weedpacket

Originally posted by ejwf
so the only thing I can assume is that there was some blank space after the ?> end tag on mysql-connect.php. would this have caused the problem?

Yes, it would (especially if it was line 20): you're including mysql-connect.php before you send your headers; so that script gets run before you send your headers. So any output on that page (which includes anything outside <?php ?> would have been output before headers were sent. Which means you would have got the error.

ejwf

thanks weedpacket
it all makes sense after all..........