When it comes to security, remember that in addition to actual platform and operating system security issues, you need to ensure that you write your application to be secure. When you write PHP applications, apply these seven habits to make sure your applications are as secure as possible:

- Validate input
- Guard your file system
- Guard your database
- Guard your session data
- Guard against Cross-Site Scripting (XSS) vulnerabilities
- Verify form posts
- Protect against Cross-Site Request Forgeries (CSRF)