Web Programming

Clients and Server

•  Web programming languages are usually classified as server-side or client-side. Some languages, such as JavaScript, can be used as both client-side and server-side languages, but most Web programming languages are server-side languages. 
• The client is the Web browser, so client-side scripting uses a Web browser to run scripts. The same script may produce different effects when different browsers run it. 
• A Web server is a combination of software and hardware that outputs Web pages after receiving a request from a client. Server-side scripting takes place on the server. If you look at the source of a page created from a server-side script, you'll see only the HTML code the script has generated. The source code for the script is on the serverand doesn't need to be downloaded with the page that's sent back to the client.
• Web Programming Languages:

1. PHP
2. ASP
3. Perl
4. Java Script

Client/Server Interaction

For Web pages, the client requests a page the server returns it:there’s no permanent connection, just a short conversation.
Details of the conversation are specified by HTTP.

Server-Side

•   PHP is a Server-side language
•  Even though it is embedded in HTML files much like the client-side Javascriptlanguage, PHP is server-side and all PHP tags will be replaced by the server before anything is sent to the web browser. 

• So, if the HTML file contains any PHP(or any script langauge) code,  Then user will get just simple html code.