MySQL and mSQL

Important Considerations for CGI Scripts

Now you have seen the basic operation of a CGI transaction: a client sends information, usually via form data, to the web server. The server then executes the CGI program, passing it the information. The CGI program then performs its magic and sends the output back to the server, where it is relayed to the client. From this point, you must make the leap from understanding how a CGI program works to understanding what makes them so popular.

While you’ve seen enough in this chapter to put together a rudimentary working CGI program, there are some critical topics you should learn before putting together real programs with MySQL or mSQL. First, you have to learn how to support multiple forms. You also need to study some security features that prevent malicious users from snooping or removing files on your site.

State Retention

Although it sounds like something done to hardened criminals, state retention is really a vitally important tool in providing advanced services to your users. The problem is this: HTTP is what is known as a `stateless’ protocol. That is, the client sends a request to the server, the server returns data to the client and both go their separate ways. The server keeps no special information about the client that would aid it in any future transactions. Likewise, there is no guarantee the client will remember anything about the transaction that it could use later. This puts an immediate and significant restriction on the usability ...