PHP Cookies Tutorial

1. What are Cookies?

Cookies are used to store user preferences, session data, and tracking information. They are sent to the client and then sent back to the server with each request.

2. Setting Cookies

To set a cookie in PHP, use the setcookie() function. This function must be called before any output is sent to the browser.

// Example of setting a cookie
setcookie("user", "John Doe", time() + (86400 * 30), "/"); // 86400 = 1 day
// The cookie will expire in 30 days.

3. Reading Cookies

To read a cookie, access the $_COOKIE superglobal array. This array holds all the cookies sent by the client to the server.

// Example of reading a cookie
if(isset($_COOKIE["user"])) {
    echo "Welcome back, " . $_COOKIE["user"] . "!";
} else {
    echo "Hello, Guest!";
}

4. Deleting Cookies

To delete a cookie, set its expiration time to a past timestamp using the setcookie() function.

// Example of deleting a cookie
setcookie("user", "", time() - 3600, "/"); // Expire the cookie immediately

5. Advanced Cookie Techniques

Cookies can also store more complex data, such as arrays or objects, by serializing them.

// Example of storing an array in a cookie
$userData = array("name" => "John", "age" => 30);
setcookie("userData", serialize($userData), time() + (86400 * 30), "/");

// To retrieve and unserialize the data
if(isset($_COOKIE["userData"])) {
    $userData = unserialize($_COOKIE["userData"]);
    echo "Name: " . $userData["name"] . ", Age: " . $userData["age"];
}

6. Security Considerations

When working with cookies, consider the following best practices:

• Use the HttpOnly and Secure flags to enhance cookie security.
• Avoid storing sensitive information directly in cookies.
• Implement proper validation and sanitation when retrieving cookie data.

Conclusion

Cookies are a powerful tool for managing user sessions and preferences in PHP. Understanding how to set, read, and delete cookies effectively will enhance your web applications.