Working with Cookie Variables

Cookies are general variables used by application servers such as ColdFusion Server to store data in and retrieve data from individual browsers.

As shown in the variable scope table above, a cookie is available from a specific browser to a specific server across sessions. This means that the cookie variables that you set in an individual browser can be referenced in different application pages.

For example, you may create a cookie and send it back to the browser during a user's login. That way, you can reference the cookie to pass specific data from page to page and each time the browser returns to the application. This is extremely important to site personalization strategies.

Cookies are characterized as:

Persistent - they stay stored in the browser until they expire or are deleted.
Widely-supported - almost all commercial browsers support them.
Domain specific - they are set and retrieved for a specific server, such as www.allaire.com or 127.0.0.1.

20 cookies can be set in a user's browser for each domain. ColdFusion Server reserves two of these cookies, for CFID and CFTOKEN.

Create cookies using either the CFCOOKIE tag or the CFSET tag on an application page. When you create a cookie:

It is set on the client after the entire page is processed.
You can set it to expire.
You can delete it later if you want to.
It persists until the browser is closed unless you set it to expire.

Note:

Use Secure Sockets Layer (SSL), to exchange cookies securely.

Setting Cookies example

The code below creates the cookie variable, User_ID, assigns it a numeric value of 2344, and sets it to expire after 100 days:

<CFCOOKIE NAME="User_ID" VALUE="2344" EXPIRES="100">

Use the NAME attribute to assign the variable a name.
Use the VALUE attribute to assign the variable a value.
Use the EXPIRES attribute to assign the number of days that the cookie should live before it expires.

Optional when creating a cookie. Use a value of now to delete a cookie.

Always surround attribute values with double quotes (").

For more information on CFCOOKIE, see the CFML Language Reference for ColdFusion Express.

Referencing Cookies

Once a server stores a cookie in a browser, that cookie is automatically sent back to the server each time a page is requested by that browser. This means that you can reference that cookie as needed throughout application pages on that server.

Reference cookie variables anywhere on a page to use their values. As with any variable that you reference:

Prefix the variable name with its variable type.
Surround the variable name with pound signs (#).

Note:

Because cookies need to be set by the server before you can use them, always test whether a cookie exists before you use it in an application page.

Always prefix the cookie variable when referencing it.

Referencing Cookies example

For example, you may output a cookie's current value within another CFML tag so that you can use its value to perform conditional processing. The code below outputs the current value of the User_ID.

<CFOUTPUT>
    #Cookie.User_ID#
</CFOUTPUT>