How do I fix PHP errors, Use of undefined constant and Cannot modify header info?

Question

My website has a section where a user who has signed up for access (and has an existing profile) can edit their own profile. When the user clicks to save the profile changes, the following 4 PHP errors come up. My understanding is that often several errors appear due to the first one so I am hoping that resolving the first one is all it takes. Here I will provide details for number 1 only, rather than pasting so much code.

A PHP Error was encountered

Message: Use of undefined constant WEBMASTER - assumed 'WEBMASTER' Filename: controllers/content.php Line 285

Message: Cannot modify header info- headers already sent by (output started at ////system/core/Exceptions.php:185 Filename: libraries/Sessions.php Line 672

Message: Cannot modify header info- headers already sent by (output started at ////system/core/Exceptions.php:185 Filename: helpers/url_helper.php Line 542

Here is the code for 1. Line 285 begins with "$permission".

function edit($id="",$language=""){

    //which users are allowed to see this file.
    //* for everybody including those who are not registered
    //admin (or any other specific type for )
    $permission=array(ADMIN,WEBMASTER);
    $next_page=site_url("/content/manage");

Is there anything obviously wrong here?

it seems that `ADMIN` and `WEBMASTER` constants are not defined inside the edit function? the headers sent error will go out if you fix this problem. — Lucho, Oct 02 '15 at 14:34
You need to google for this. All these questions have been asked countless times before. — M H, Oct 02 '15 at 14:35
if you didn't define those as constants, you need to use `$permission=array("ADMIN","WEBMASTER");` - Otherwise, define them http://php.net/manual/en/function.constant.php — Funk Forty Niner, Oct 02 '15 at 14:36
@Lucho unless `ADMIN` and `WEBMASTER` are supposed to be strings (i.e. they should have quotes around them) ... — CD001, Oct 02 '15 at 14:36
If you're sending outputs before using `header`, you're going to have a bad time. — al'ein, Oct 02 '15 at 14:39
I understand that this question may have been asked several times but none of the solutions were working for me. And yes I spent several hours google 'ing'. I finally resolved it minutes ago by deleting 2 redirects that were recently wriiten into the user.php file by my programmer who has apparently fallen off the edge of the planet. Thanks to all who provided feedback. — warren44, Oct 04 '15 at 00:36

score -2 · Answer 1 · answered Oct 02 '15 at 14:34

-2

You need to define the constant:

DEFINE('WEBMASTER', 'webmaster content here')

Regarding the 'headers already sent'.... this means you are trying to modify the headers when you have already sent output to the browser.

answered Oct 02 '15 at 14:34

EquinoxMatt

79
8

score -2 · Answer 2 · answered Oct 02 '15 at 14:34

First of all, you are not allowed to modify headers after data has been sent already.

So you should put everything what modifies the header before <!doctype html>. Just make sure there is nothing before the very first <?php, even not a single space.

Example:

<?php
    // do some header modification
?>
<!doctype html>
<html xmlns="http://www.w3.org/1999/xhtml">
....
</html>

score -2 · Answer 3 · answered Oct 02 '15 at 14:34

-2

It means that there are some output in your php file before you make a redirection with function like header('Location: http://www.example.com/') ! you have to comment all "echo" "printf" or "html" before calling header function.

answered Oct 02 '15 at 14:34

modiodio

11
2

How do I fix PHP errors, Use of undefined constant and Cannot modify header info?

3 Answers3