setcookie / PHP5 Manual

Description

bool setcookie ( string name [, string value [, int expire [, string path [, string domain [, bool secure]]]]] )

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. If output exists prior to calling this function, setcookie() will fail and return FALSE. If setcookie() successfully runs, it will return TRUE. This does not indicate whether the user accepted the cookie.

Note: As of PHP 4, you can use output buffering to send output prior to the call of this function, with the overhead of all of your output to the browser being buffered in the server until you send it. You can do this by calling ob_start() and ob_end_flush() in your script, or setting the output_buffering configuration directive on in your php.ini or server configuration files.

All the arguments except the name argument are optional. You may also replace an argument with an empty string ("") in order to skip that argument. Because the expire argument is integer, it cannot be skipped with an empty string, use a zero (0) instead. The following table explains each parameter of the setcookie() function, be sure to read the Netscape cookie specification for specifics on how each setcookie() parameter works and RFC 2965 for additional information on how HTTP cookies work.

Table 1. setcookie() parameters explained

Parameter	Description	Examples
`name`	The name of the cookie.	'cookiename' is called as `$_COOKIE['cookiename']`
`value`	The value of the cookie. This value is stored on the clients computer; do not store sensitive information.	Assuming the `name` is 'cookiename', this value is retrieved through `$_COOKIE['cookiename']`
`expire`	The time the cookie expires. This is a Unix timestamp so is in number of seconds since the epoch. In other words, you'll most likely set this with the time() function plus the number of seconds before you want it to expire. Or you might use mktime().	`time()+606024*30` will set the cookie to expire in 30 days. If not set, the cookie will expire at the end of the session (when the browser closes).
`path`	The path on the server in which the cookie will be available on.	If set to `'/'`, the cookie will be available within the entire `domain`. If set to `'/foo/'`, the cookie will only be available within the `/foo/` directory and all sub-directories such as `/foo/bar/` of `domain`. The default value is the current directory that the cookie is being set in.
`domain`	The domain that the cookie is available.	To make the cookie available on all subdomains of example.com then you'd set it to `'.example.com'`. The `.` is not required but makes it compatible with more browsers. Setting it to `www.example.com` will make the cookie only available in the `www` subdomain. Refer to tail matching in the spec for details.
`secure`	Indicates that the cookie should only be transmitted over a secure HTTPS connection. When set to `TRUE`, the cookie will only be set if a secure connection exists. The default is `FALSE`.	`0` or `1`

Once the cookies have been set, they can be accessed on the next page load with the $_COOKIE or $HTTP_COOKIE_VARS arrays. Note, autoglobals such as $_COOKIE became available in PHP 4.1.0. $HTTP_COOKIE_VARS has existed since PHP 3. Cookie values also exist in $_REQUEST.

Note: If the PHP directive register_globals is set to on then cookie values will also be made into variables. In our examples below, $TestCookie will exist. It's recommended to use $_COOKIE.

Common Pitfalls:

Cookies will not become visible until the next loading of a page that the cookie should be visible for. To test if a cookie was successfully set, check for the cookie on a next loading page before the cookie expires. Expire time is set via the expire parameter. A nice way to debug the existence of cookies is by simply calling print_r($_COOKIE);.
Cookies must be deleted with the same parameters as they were set with. If the value argument is an empty string, or FALSE, and all other arguments match a previous call to setcookie, then the cookie with the specified name will be deleted from the remote client.
Because setting a cookie with a value of FALSE will try to delete the cookie, you should not use boolean values. Instead, use 0 for FALSE and 1 for TRUE.
Cookies names can be set as array names and will be available to your PHP scripts as arrays but separate cookies are stored on the users system. Consider explode() to set one cookie with multiple names and values. It is not recommended to use serialize() for this purpose, because it can result in security holes.

In PHP 3, multiple calls to setcookie() in the same script will be performed in reverse order. If you are trying to delete one cookie before inserting another you should put the insert before the delete. As of PHP 4, multiple calls to setcookie() are performed in the order called.

Some examples follow how to send cookies:
Example 1. setcookie() send example
<?php $value = 'something from somewhere'; setcookie("TestCookie", $value); setcookie("TestCookie", $value, time()+3600); /* expire in 1 hour */ setcookie("TestCookie", $value, time()+3600, "/~rasmus/", ".example.com", 1); ?>

Note that the value portion of the cookie will automatically be urlencoded when you send the cookie, and when it is received, it is automatically decoded and assigned to a variable by the same name as the cookie name. If you don't want this, you can use setrawcookie() instead if you are using PHP 5. To see the contents of our test cookie in a script, simply use one of the following examples:


<?php
// Print an individual cookie
echo $_COOKIE["TestCookie"];
echo $HTTP_COOKIE_VARS["TestCookie"];

// Another way to debug/test is to view all cookies
print_r($_COOKIE);
?>

When deleting a cookie you should assure that the expiration date is in the past, to trigger the removal mechanism in your browser. Examples follow how to delete cookies sent in previous example:

Example 2. setcookie() delete example
<?php // set the expiration date to one hour ago setcookie ("TestCookie", "", time() - 3600); setcookie ("TestCookie", "", time() - 3600, "/~rasmus/", ".example.com", 1); ?>

You may also set array cookies by using array notation in the cookie name. This has the effect of setting as many cookies as you have array elements, but when the cookie is received by your script, the values are all placed in an array with the cookie's name:

Example 3. setcookie() and arrays
<?php // set the cookies setcookie("cookie[three]", "cookiethree"); setcookie("cookie[two]", "cookietwo"); setcookie("cookie[one]", "cookieone"); // after the page reloads, print them out if (isset($_COOKIE['cookie'])) { foreach ($_COOKIE['cookie'] as $name => $value) { echo "$name : $value <br />\n"; } } ?>
which prints
three : cookiethree two : cookietwo one : cookieone

Note: The following RFC's may also be useful: RFC 2109 and RFC 2695
You may notice the expire parameter takes on a Unix timestamp, as opposed to the date format Wdy, DD-Mon-YYYY HH:MM:SS GMT, this is because PHP does this conversion internally.
expire is compared to the client's time which can differ from server's time.

Note: Microsoft Internet Explorer 4 with Service Pack 1 applied does not correctly deal with cookies that have their path parameter set.
Netscape Communicator 4.05 and Microsoft Internet Explorer 3.x appear to handle cookies incorrectly when the path and time are not set.

See also header(), setrawcookie() and the cookies section.