setcookie, Cannot modify header information - headers already sent
I am new to PHP, I practised PHP setcookie() just now and failed.
http://localhost/test/index.php
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title></title>
</head>
<body>
<?php
$value = 'something from somewhere';
setcookie("TestCookie", $value);
?>
</body>
</html>
http://localhost/test/view.php
<?php
// I plan to view the cookie value via view.php
echo $_COOKIE["TestCookie"];
?>
But I failed to run index.php, IE warning like this.
Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\test\index.php:9) in C:\xampp\htdocs\test\index.php on line 12
I enabled my IE 6 cookie no doubt.
Is there anything wrong on my procedure above? Thank you.
WinXP OS and XAMPP 1.7.3 used.
Answer
The warning is clear.
Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\test\index.php:9) in C:\xampp\htdocs\test\index.php on line 12
Cookies are sent in the HTTP response header. Since the HTML content already started, you cannot go back to the header and add the cookie.
From http://php.net/setcookie:
setcookie() defines a cookie to be sent along with the rest of the HTTP headers. Like other headers, cookies must be sent before any output from your script (this is a protocol restriction). This requires that you place calls to this function prior to any output, including
<html>and<head>tags as well as any whitespace.
Move that setcookie statement before any HTML appears:
<?php
$value = 'something from somewhere';
setcookie("TestCookie", $value);
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
....