Developing State-enabled Applications With PHP
By John L.2006-08-30
Cookies
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Cookies are used to store State-information in the browser. Browsers are allowed to keep up to 20 cookies for each domain and the values stored in the cookie cannot exceed 4 KB. If more than 20 cookies are created by the website, only the latest 20 are stored. Cookies are only suitable in instances that do not require complex session communications and are not favoured by some developers because of privacy issues. Furthermore, some users disable support for cookies at their browsers.
The following is a typical server-browser sequence of events that occur when a cookie is used:
1. The server knows that it needs to remember the State of browsing session
2. The server creates a cookie and uses the Set-Cookie header field in the HTTP response to pass the cookie to the browser
3. The browser reads the cookie field in the HTTP response and stores the cookie
4. This cookie information is passed along future browser-server communications and can be used in the PHP scripts as a variable
PHP provides a function called setcookie() to allow easy creation of cookies. The syntax for setcookie is: int setcookie(string name, [string val], [int expiration_date], [string path], string domain, [int secure])
The parameters are:
1. name - this is a mandatory parameter and is used subsequently to identify the cookie
2. value - the value of the cookie - e.g. if the cookie is used to store the name of the user, the value parameter will store the actual name - e.g. John
3. expiration_date - the lifetime of the cookie. After this date, the cookie expires and is unusable
4. path - the path refers to the URL from which the cookie is valid and allowed
5. domain - the domain the created the cookie and is allowed to read the contents of the cookie
6. secure - specifies if the cookie can be sent only through a secure connection - e.g. SSL enable sessions
The following is an example that displays to the user how many times a specific web page has been displayed to the user. Copy the code below (both the php and the html) into a file with the .php extension and test it out.
[?php //check if the $count variable has been associated with the count cookie if (!isset($count)) {
$count = 0; } else {
$count++; } setcookie("count", $count, time()+600, "/", "", 0); ?]
[html]
[head]
[title]Session Handling Using Cookies[/title]
[/head]
[body]
This page has been displayed: [?=$count ?] times.
[/body] [/html]
The next installment discusses how to manage sessions using PHP session handling functions with cookies enabled...
Tutorial Pages:
» Developing State-enabled Applications With PHP
» Cookies
» PHP Session Handling - Cookies Enabled
» PHP Session Handling - Without Cookies
