Subtitles of the Movie

In this movie I’m going to explain a little of the way data moves around with the dynamic website and how this differs from static web pages that you’re probably very used to creating. The different elements we’re going to look at are the user's machine, which is connected to the Internet and the server, in this case an application server and this differs from a standard web server in that the web server will only serve what ever it’s asked for and the data that's stored on a web server is all completely pre packaged as html pages or even if it’s, even if the data seems more complex and dynamic for instance if it serves Java script or Flash movies. All of that is essentially static in that the user simply requests a particular page and gets the content in the form that it's arranged on the server. An application server however can run a script when that's requested by the user and through the inputs that the user has returned to the application server, it can make dynamic and more intelligent choices about the kind of content that the user wants to see. It can work with conjunction with database server and although these are usually separate, it’s quite possible that there might only actually be one machine with an application and database server effectively in the same box but they’re different concepts, so even if they are physically together, its best to look at them as two separate entities. So what happens basically when the user types in the url of whatever page they’re calling on the Internet is that the request is passed to the application server and that's the point at which php comes in. The scripts that we run on the application server to allow the content to be served in dynamic way based on the users choices and what we know about the user, are written in a variety of different scripts. Obvious examples are Microsoft's active server pages which use V.B script and J script, other examples will be Pearl or Java server pages or Cold Fusion. We’re looking at PHP and all of these tools although they do things in some areas better than others, they all fulfill this same kind of purpose, running a script on the application server. So this is where the technology that we’re going to be looking at throughout this title php comes in the scripts that are run on the application server. These scripts may then request based on the information that has been passed on by the user, information from the database server and the database server sends back information to the php script which then serves the data up in an acceptable form to be handed back to the user. Now all the way through this title, we’re just going to be looking at serving pure html. It is perfectly possible to serve other kinds of technology such as Java script or client side scripting through php but typically we’re going to be serving up html. It’s also possible to pass information to a client side application, for instance I do a lot of that with Macromedia flash sending information from php to Macromedia flash, how ever at it’s simplest form, php will serve html which is readable in any browser on the users machine. A distinction I should make here is between server side scripting such as php or any of the other technologies I just mentioned and client side scripting such as most typical example would be Java script, other examples would be, these wouldn't be scripting as such but such things as java applets that run on the users browser through the Java virtual machine or Flash movies. Now these are client side, client side scripts or applets and this should not be confused with the job that is done by php, which is a server side technology. So the content is returned via the Internet to the users machine based on their choices and the structure that we setup in our php scripts. This is basically how the dynamic web works.