Working with security flaws is interesting, sometimes even funif you do not happen to find the traces of these flaws on your own system. More information about these possible issues are available in the PHP manual's section on security. Visiting the Open Web Application Security Project (OWASP) is also recommended; its home page is www.owasp.org. This Open Source initiative informs about common security flaws and how to address them in the Web.
In this chapter, you learned about securing a website from outside access (only known users may access the page) and also from within (careful programming techniques in the code do not allow anybody to do any harm to the Web application and the Web server). The next chapter deals with a similar topic, data encryption.