cannot modify header

PaulaRun

I'm getting a cannot modify header error on my script. When I do a view source, I see <br />. I can't figure out where that is coming from. Does anybody know how I can find it? This one has really got me stumped.

Thanks for any help!

Mordecai

The <br />'s probably from the error, actually. When it's printed out, it likes to be on its own line.

PaulaRun

I thought that was causing the error. I'm really getting confused now. I thought that the error was caused by whitespace before the header().

Mordecai

If there is whitespace before the header, it will cause the error. If you don't see anything, chances are it's whitespace. If you look at the error, it will tell you where output starts.

PaulaRun

I'm ready to give up. There is NO whitespace before the header!

Here is the code before the header:

<html>
<head>
<title></title>
</head>
<body>
<?
#########################################################
#                                                       #
#  Program         : IPN Development Handler            #
#  Author          : Marcus Cicero                      #
#  File            : notify.php                         #
#  Function        : Skeleton IPN Handler               #
#  Version         : 1.5                                #
#  Last Modified   : 01/14/2003                         #
#  Copyright       : EliteWeaver UK                     #
#                                                       #
#########################################################
#    THIS SCRIPT IS FREEWARE AND IS NOT FOR RE-SALE     #
#########################################################


// IPN Posting Modes, Choose: 1 or 2

$postmode = "2";

       //* 1 = Live Via PayPal Network
       //* 2 = Test Via EliteWeaver UK


// Convert Super globals on Older PHP builds

        if(phpversion() <= "4.0.6")
        {
               $_POST = ($HTTP_POST_VARS);
                              }

// No IPN post Means this Script does Not exist :)

        if (!$_POST['txn_type'])
        { header("Status: 404 Not Found"); exit;
                              }
        else
        { header("Status: 200 OK");
                              }

Here is the error:

Warning: Cannot modify header information - headers already sent by (output started at /home/dexter/public_html/notify.php:6) in /home/dexter/public_html/notify.php on line 40

Line 6 is <?
Line 40 is { header("Status: 200 OK");

Mordecai

Nope, there's lots of HTML.
<html>
<head>
<title></title>
</head>
<body>
<? ...

Gargouil

that's right

when using a header() function you should not have any (space, carriage return, html code) before his call

put you few html basile after your header... cause anyway if you redirect to another page, this is useless to send html to the page 🙂

dalecosp

Originally posted by PaulaRun
I'm ready to give up. There is NO whitespace before the header!

Here is the

output // edit

code before the header:

<html>
<head>
<title></title>
</head>
<body>[/b][/quote]

PaulaRun

How can I have the PHP code without the HTML?? I thought PHP had to be in an HTML page?

superwormy

You have to put the HTML AFTER the header() is sent, or use output buffering:

www.php.net/ob_start

PaulaRun

For my example, can I do this?

if (!$_POST['txn_type'])
            { header("Status: 404 Not Found"); exit;
                                  }
            else
            { header("Status: 200 OK");
                                  }
[/php}

<html> 
<head> 
<title></title> 
</head> 
<body> 
<? ...the rest of the script??

superwormy

Should be able to, don't see why not.

As a note, you don't need to send the 200 OK header, thats what it is already assumed to be.

PaulaRun

Thanks, that worked! I appreciate you taking the time to explain it to me!!

dalecosp

Originally posted by PaulaRun
How can I have the PHP code without the HTML?? I thought PHP had to be in an HTML page?

Not necessarily. Consider:

<?php
 echo "<html>\n<head><title>";
echo "My PHP Page</title>\n</head>";
echo "<body>\nThis is my page about PHP,  Hope you like it.\n<br>\n<br>";
echo "\n</body>\n</html>";
?>

PHP is rather good at producing HTML output. However, it's a little slower to use print() or echo() to just output HTML, and it's a waste (why not just use HTML?) so most people mix the two.

OTOH, once a script is called, the PHP parser will execute code whether it's any kind of 'output' to the browser or not; and, as you found out, certain functions, like header(), setcookie() and session_start() ONLY work when nothing has yet been output to the browser (any text of any kind, whether actually code, or even just a space, which also has an ASCII value). So, as a general rule, always start your scripts/pages with enough PHP code to handle all possible branches of the logic tree before you start writing browser output.