Cookies vs Sessions in PHP – Key Differences (5-Line Description):
Cookies are stored in the user’s browser, while sessions are stored on the server.
Cookies are less secure and suitable for storing small, non-sensitive data like preferences.
Sessions are more secure and ideal for storing sensitive data like login credentials.
Cookies have size and storage limitations; sessions do not.
Sessions require starting with session_start(), whereas cookies use setcookie().
Comparison Table:
| Feature | Cookies | Sessions |
|---|---|---|
| Storage | Stored on the client’s browser | Stored on the server |
| Security | Less secure (can be modified by user) | More secure (data hidden from user) |
| Size Limit | About 4KB max | Virtually unlimited |
| Lifetime | Can persist until expiry (even after browser close) | Typically ends when browser is closed or manually destroyed |
| Access | Accessible via $_COOKIE |
Accessible via $_SESSION |
| Use Case | Store non-sensitive data like theme, language | Store sensitive data like login info |
| Speed | Slightly faster (no server processing needed) | Slightly slower (data stored server-side) |
| Tracking | Used for remember me, tracking users | Used for login sessions, carts, etc. |
When to Use What:
- Cookies: For remembering user preferences, themes, or simple identifiers.
- Sessions: For login systems, shopping carts, or any sensitive user data.
Example Code:
Set Cookie:
login.php
setcookie("user", "John", time() + 3600); // 1 hour
Set Session:
login.php
session_start();
$_SESSION['user'] = "John";
