Cannot modify header information [duplicate] - php

Question

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Headers already sent by PHP
I am getting the following error from the following code, and I am not entirely sure why. If you could tell me how to fix it, that would be great. Thanks in advanced.
Warning: Cannot modify header information - headers already sent by (output started at...) on line 45.
<?php
// Initialization
$conn = mysql_connect(DB_HOST,DB_USER,DB_PASSWORD);
mysql_select_db(DB_NAME, $conn);
// Error checking
if(!$conn) {
die('Could not connect ' . mysql_error());
}
// Localize the GET variables
$ref = isset($_GET['ref']) ? $_GET['ref'] : "";
// Protect against sql injections
// Insert the score
$retval = mysql_query("INSERT INTO $table(
site
) VALUES (
'$ref'
)",$conn);
if($retval) {
echo "Successfull";
} else {
echo "Unsuccessfull " . mysql_error();
}
mysql_close($conn);
?>
<?php
$url = $_GET['url'];
$loc = 'Location: '. $url;
header($loc);
exit;
?>

Answer 1

Take out the echo calls, you can't send information to the browser before the headers.
You can try something like this to still show if an error happens:
if(!$retval) {
echo "Unsuccessfull " . mysql_error();
}

Answer 2

If you change the headers you cannot output any text prior to to the header command otherwise the headers will already be sent.
ie.
if($retval) {
echo "Successfull";
} else {
echo "Unsuccessfull " . mysql_error();
}
Is outputting text before you change the headers.

Answer 3

Use Output Buffers: http://php.net/manual/en/function.ob-start.php
ob_start();
at the start and
ob_end_flush();
at the end.

Answer 4

What I generally recommend for situations like this, is save all output to the end, as gmadd mentioned, you can do the ob_start, but I prefer to store the data in a string without having to add the extra code (I know you can also designate this in the .htaccess file, I would go that route over adding the actual ob_start items).
What I would do:
$display = ""; // initiate the display string
// etc doe here
if($retval) {
$display .= "Successfull";
} else {
$display .= "Unsuccessfull " . mysql_error();
}
// end of the script right before ?>
echo $display;
?>
The ob_start method works and if you want to go that route, you can add this in the .htaccess file (given that allowoverride is set in your apache setup):
php_value output_buffering On
Again I still recommend the $display storage method, but that is my personal opinion.

Answer 5

Use:
<meta http-equiv="Refresh" content="0;url=http://www.example.com" />