Flex is a highly productive, free open source framework for building and maintaining expressive web applications that deploy consistently on all major browsers, desktops, and operating systems. While Flex applications can be built using only the free open source framework, developers can use Adobe® Flex® Builder™ software to dramatically accelerate development.
Flex is very versatile in its use and implementation. It can used with variety of server side technologies like Java, PHP, Cold-Fusion etc. Flex provides three types of Remote procedure Call Services to interact with the server. These RPC’s are Web-Services which makes soap calls to the server, HTTP service calls send HTTP request and responses. And Remote Object call service which send binary call using HTTP request packets via AMF3 protocols. The remote object call is the fastest service call to the remote servers as the it provides the simplest de serialization, since the data transfer is in binary format which flash player understands easily.
Use of Flex in Web Applications