Cannot modify header information

saidbakr

Hi,
This message appears with some code:
Warning: Cannot modify header information - headers already sent by (output started at f:\teachphp\pdfclass\del.php:2) ...
What's this message mean? and How can I avoid it.
I use PHP 4.3
On Apache 1.3.26
win Me😕

echo

This is usually due to some code which tries to change the header info of the document after it has been set.
Look for setting cookies or calling the header(location) function after something has been output to the browser (even a single whitespace before your opening <?php tag will do it).

saidbakr

To be more specific, this warning message appears when I use a code like this,

<?php
include ('class.ezpdf.php');
$pdf =& new Cezpdf();
$pdf->selectFont('./fonts/Helvetica.afm');
$data = array(
array('num'=>1,'name'=>'gandalf','type'=>'wizard')
,array('num'=>2,'name'=>'bilbo','type'=>'hobbit','url'=>'http://www.ros.co.
nz/pdf/')
,array('num'=>3,'name'=>'frodo','type'=>'hobbit')
,array('num'=>4,'name'=>'saruman','type'=>'bad
dude','url'=>'http://sourceforge.net/projects/pdf-php')
,array('num'=>5,'name'=>'sauron','type'=>'really bad dude')
);
$pdf->ezTable($data);
$pdf->ezStream();
?>

So from your reply, you mean I should to insert a white line between <?php and the rest of the code?

kriek

Use output buffering with ob_start() and ob_end_flush()

<?php ob_start(); ?>

// entire script, code, or page here

<?php ob_end_flush(); ?>

Although ob_end_flush() isn't needed in MOST cases because it is called automatically at the end of script execution by PHP itself when output buffering is turned on either in the php.ini or by calling ob_start() If you have anymore questions on this topic don't hesitate to ask. Ciao!

saidbakr

Thank you for your reply so much and I will try your advice soon🙂

kriek

No problem. Output buffering (PHP 4.0) was originally designed to solve HTTP header errors. I should also mention that Output buffers are stackable, that is, you may call ob_start() while another ob_start() is active. Just make sure that you call ob_end_flush() the appropriate number of times. If multiple output callback functions are active, output is being filtered sequentially through each of them in nesting order.

altexis

This smells like a classic session problem

Do you use sessions? kriek's solution is the most hard-core you could use, but before you do it... just try this:

put this line in the beggining of your page (even before the starting <html> tag):
<? session_start(); ?>

leave the rest as it is

kriek

Originally posted by altexis
kriek's solution is the most hard-core you could use

Output buffering is not hardcore by any means. It's a practical, functional, and easy solution to most HTTP header errors. While output buffering is active no output is sent from the script except headers, instead the output is stored in an internal buffer.

Zend » Zeev Suraski

Developer Shed » Harish Kamath

saidbakr

Hi,
I'd like to mention that I'm not use session at all. I just try to test code depends on some PHP extensions and classes to produce things such as pdf or images.
This problem did not displayed before using this classes and extensions in using the elder version of PHP I use now version 4.3 and I use dlls of extensions from phpdev4.3. on Apache 1.3.26.
Now I'd like to ask, if there a bit of settings in php.ini may solve this warning error?
My OS is MS Win ME

diego25

Use kriek's solution -- output buffering.

Diego