Home
>
Web Development
>
Developing State-enabled Applications With PHP

Developing State-enabled Applications With PHP

Installment 1

When a user is browsing through a website and is surfing from one web page to another, sometimes the website needs to remember the actions (e.g. choices) performed by the user. For example, in a website that sells DVDs, the user typically browses through a list of DVDs and selects individual DVDs for check out at the end of the shopping session. The website needs to remember which DVDs the user has selected because the selected items needs to be presented again to the user when the user checks out. In other words, the website needs to remember the State - i.e. the selected items - of the user's browsing activities.

However, HTTP is a Stateless protocol and is ill-equipped to handle States. A standard HTML website basically provides information to the user and a series of links that simply directs the user to other related web pages. This Stateless nature of HTTP allows the website to be replicated across many servers for load balancing purposes. A major drawback is that while browsing from one page to another, the website does not remember the State of the browsing session. This make interactivity almost impossible.

In order to increase interactivity, the developer can use the session handling features of PHP to augment the features of HTTP in order to remember the State of the browsing session. The are basically 2 ways PHP does this:

1. Using cookies
2. Using Sessions

The next installment discusses how to manage sessions using cookies...

Installment 2

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...

Installment 3

PHP Session Handling - Cookies Enabled

Instead of storing session information at the browser through the use of cookies, the information can instead be stored at the server in session files. One session file is created and maintained for each user session. For example, if there are three concurrent users browsing the website, three session files will be created and maintained - one for each user. The session files are deleted if the session is explicitly closed by the PHP script or by a daemon garbage collection process provided by PHP. Good programming practice would call for sessions to be closed explicitly in the script.

The following is a typical server-browser sequence of events that occur when a PHP session handling is used:

1. The server knows that it needs to remember the State of browsing session

2. PHP generates a sssion ID and creates a session file to store future information as required by subsequent pages

3. A cookie is generated wih the session ID at the browser

4. This cookie that stores the session ID is transparently and automatically sent to the server for all subsequent requests to the server

The following PHP session-handling example accomplishes the same outcome as the previous cookie example. Copy the code below (both the php and the html) into a file with the .php extension and test it out.

[?php //starts a session session_start();

//informs PHP that count information needs to be remembered in the session file if (!session_is_registered("count")) {

session_register("count");

$count = 0; } else {

$count++; }

$session_id = session_id(); ?]

[html]

[head]

[title]PHP Session Handling - Cookie-Enabled[/title]

[/head]

[body]

The current session id is: [?=$session_id ?]

This page has been displayed: [?=$count ?] times.

[/body] [/html]

A summary of the functions that PHP provides for session handling are:

1. boolean start_session() - initializes a session

2. string session_id([string id]) - either returns the current session id or specify the session id to be used when the session is created

3. boolean session_register(mixed name [, mixed ...]) - registers variables to be stored in the session file. Each parameter passed in the function is a separate variable

4. boolean session_is_registered(string variable_name) - checks if a variable has been previously registered to be stored in the session file

5. session_unregister(string varriable_name) - unregisters a variable from the session file. Unregistered variables are no longer valid for reference in the session.

6. session_unset() - unsets all session variables. It is important to note that all the variables remain registered.

7. boolean session_destroy() - destroys the session. This is opposite of the start_session function.

The next installment discusses how to manage sessions using PHP session handling functions when cookies are disabled...

Installment 4

PHP Session Handling - Without Cookies

If cookies are disabled at the browser, the above example cannot work. This is because although the session file that stores all the variables is kept at the server, a cookie is still needed at the browser to store the session ID that is used to identify the session and its associated session file. The most common way around this would be to explicitly pass the session ID back to the server from the browser as a query parameter in the URL.

For example, the PHP script generates requests subsequent to the start_session call in the following format: http://www.yourhost.com/yourphpfile.php?PHPSESSID=[actual session ID]

The following are excerpts that illustrate the discussion:

Manually building the URL:
$url = "http://www.yoursite.com/yourphppage.php?PHPSESSID=" . session_id(); [a href="[?=$url ?]"]Anchor Text[/a]

Building the URL using SID:
[a href="http://www.yoursite.com/yourphppage.php?[?=SID ?]"]Anchor Text[/a]

Used with the author's permission.

This article is written by John L.
John L is the Webmaster of designer banners (designer banners).

maid service near Lake Forest ..

In The News:

New phishing platform QRR targets Microsoft 365 users across 1,000 domains in 90 countries. Learn how to spot fake login pages and protect your accounts.

OpenTable now uses AI to track your dining habits and share insights with restaurants. Learn what data they collect and how to protect your privacy.

Google's discontinued Nest thermostats still secretly upload home data to company servers despite losing smart features, raising serious privacy concerns.

New Android malware NGate steals NFC payment codes in real-time, allowing criminals to withdraw cash from ATMs without your card. Learn protection tips.

DoorDash confirms data breach exposing customer names, emails, addresses after social engineering attack. Learn how to protect yourself from scams.

Concerned about Google's AI scanning your Gmail? Learn how to disable Gemini features that access your emails, Drive files and Chat messages for privacy.

Google warns Android users about dangerous fake VPN apps hiding malware that steals passwords, banking details and personal data from phones and tablets.

Apple's digital passport feature lets iPhone users breeze through TSA checkpoints this holiday season using Digital ID technology at 250+ airports.

A new phishing scam targets family photos with fake "Cloud Storage Full" alerts. Criminals steal credit card information through fake sites. Learn protection tips.

South Korean scientists create ultra-thin fabric muscles that turn clothes into robotic assistants, lifting 33 pounds while weighing under half an ounce.

Archer Aviation has acquired Hawthorne Airport for $126M to launch an LA air taxi network ahead of the 2028 Olympics, featuring AI-powered eVTOL operations and next-gen aviation tech.

Stay up to date on the latest AI technology advancements and learn about the challenges and opportunities AI presents now and for the future.

Fake AI apps disguised as "ChatGPT" and "DALL·E" are flooding app stores with dangerous malware that steals data and monitors users without detection.

Fake buyers demand specific vehicle reports from unknown sites to steal credit card information from car sellers, but warning signs can help identify these scams before paying.

Android users can now manage apps across multiple devices more easily with Google Play Store's updated remote uninstall button in the latest update.

NASA's Perseverance rover discovers shiny metallic rock on Mars that could be a meteorite from an ancient asteroid, containing high levels of iron and nickel.

Holiday scams spike during Black Friday and Cyber Monday as criminals exploit your leaked personal data. Learn how to protect yourself from fake stores and phishing.

Commerce Department proposes TP-Link router ban over Chinese security risks. Learn how this potential prohibition could affect your home network and devices.

Hyundai AutoEver America suffered a data breach affecting 2,000 current and former employees, exposing names, Social Security numbers and driver's license information.

Washington court rules automated license plate reader images are public records, even when stored by vendors like Flock Safety, setting precedent for transparency.

Fake airline texts claiming flight cancellations are targeting travelers with convincing scams. Learn how cybercriminals steal personal data and credit card info.

Discover how iOS 26's new Adaptive Power feature automatically extends iPhone battery life by learning your usage patterns and adjusting performance intelligently.

New TikTok malware campaign tricks users into running PowerShell commands that download Aura Stealer, which steals credentials and authentication tokens.

Gaia Family offers fixed upfront pricing for IVF cycles with unlimited embryo transfers and financial protection, partnering with over 100 U.S. fertility clinics.

The Jetsons Act aims to position Pennsylvania as a leader in advanced air mobility by establishing regulations for hybrid ground-air vehicles.

Developing State-enabled Applications With PHP

Web Development