Question

I’m trying to set a cookie in wordpress. I have my cookie set like this :

<?php setcookie('test', 'test', 0, '/', '/');  ?>

in header.php of my theme, but when I go to my browser to view my website I get this error

Warning: Cannot modify header information - headers already sent by (output started at /home/content/19/9468119/html/wp-content/themes/twentyeleven/header.php:27) in /home/content/19/9468119/html/wp-content/themes/twentyeleven/header.php on line 201

and also my cookie doesnt set. How do I set a cookie in wordpress?

I have also tried this

 function set_new_cookie() {
    setcookie('test', 'test', 0, '/', '/');
}
add_action( 'init', 'set_new_cookie');

Answer 1

You have to set them before anything is outputted

look there: How can I set, get and destroy cookies in WordPress?

If you are using a theme in function.php

function set_new_cookie() {
    //setting your cookies there
}
add_action( 'init', 'set_new_cookie');

Your expiration date is 0 so you cookies will be deleted right away look at the php doc:

EDIT:
From php.net:

If set to 0, or omitted, the cookie will expire at the end of the
session (when the browser closes).

http://php.net/manual/en/function.setcookie.php

You have to set it like this for example :

setcookie("TestCookie", $value, time()+3600);  /* expire in 1 hour */