As a php developer, you need to understand the difference between an application server and a web server. A web server processes only HTTP requests, while an application server serves business logic to application programs through an unlimited number of protocols. A web server is a program that accepts requests for information and sends the required documents. An application server may be a program or a computer running a program in a distributed network.
The application server
An application server exposes business logic to client applications through various protocols, including possibly HTTP. While a Web server deals primarily with sending HTML code for display in a web browser, an application server provides access to business logic for use by client application programs.
In most cases, the server exposes this business logic through a component API, such as the Enterprise JavaBean (EJB) component on the Java 2 Platform, Enterprise Edition (J2EE) application servers. In addition, the application server manages its own resources. These security tasks include security, transaction processing, resource pooling, and messaging. Just like a Web server, an application server can also use a variety of scalability and fault tolerance techniques.
Operation of Web
The dialogue between a server program and a client program is done according to specific rules that constitute a protocol. The web protocol is HTTP.
Any web site consists, materially, of a machine connected to the Internet equipped with the server program running permanently on this computer. The server program is waiting for requests sent to its attention on the network by a client program. When a request is received, the server program analyzes it to determine what the requested document is, searches for that document, and passes it to the client program. Another important type of interaction is for the client program to ask the server program to run a program, based on parameters, and to transmit the result to it.
An application server can contain a Web server, which means that it can perform operations performed by a Web server, as well as additional elements and features to facilitate grouping of connections, grouping objects, support transactions, etc.