trouble in using include and header in php. "Cannot modify header information"

Question

i have a file 'header.php' which has a search text box in it. Another file called 'myPage.php' includes 'header.php'. In header.php

 if (isset($_POST['Searchbutton'])){ // this will execute when the search button is clicked.
 $target = $_POST['searchtext'];
 header("Location: searchresult.php?text=" . $target); // line #8
 }

In myPage.php

<?php
include("header.php");
?>

When i'm on "myPage.php" and use the search option, i get an error that says

Cannot modify header information - headers already sent by (output started at myPage.php:3) in header.php on line 8.

Can anyone please help me understand the concept. I'm a newbie to php. Please ask if any more info is required.

Cheers!

Don't output anything before using `header()` – Mr. Alien Apr 18 '13 at 18:50 — Mr. Alien, Apr 18 '13 at 18:50

score 0 · Answer 1 · answered Apr 18 '13 at 18:52

0

You can not output something to the browser before you send a header(). Just have a look at how http works and you'll understand :)

http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol#Client_request

answered Apr 18 '13 at 18:52

pmayer

341
2
13

score 0 · Answer 2 · answered Apr 18 '13 at 18:53

In short, what you're trying to do doesn't make sense. When you send a page, you also send the HTTP headers with it. You are trying to send a page, then send a header that redirects the client to another page.

This is why you get the headers already sent error. Since you're just trying to post a form, there is no reason to try and redirect... simply have the target of the form be the script that processes the search criteria.

score 0 · Answer 3 · answered Apr 18 '13 at 18:56

0

header() can not be called if anything has already been output to the browser. You can avoid this problem with ob_start() at the beginning of the code, and then ob_flush() where you want to send the output. This will buffer all the output to the browser until ob_flush() is called.

This also means that header() redirects, or other changes can be made as long as they occur before ob_flush()

answered Apr 18 '13 at 18:56

Camron

308
1
7

There is no reason to buffer output in this scenario. – gview Apr 18 '13 at 19:49

trouble in using include and header in php. "Cannot modify header information"

3 Answers3