Loading, unloading, and requests

As the Zend engine runs, it processes one or more "requests" from its client. In the traditional CGI implementation, this corresponds to one execution of a process. However, many other implementations, most notably the Apache module, can map many requests onto a single PHP process. A Zend extension may thus see many requests in its lifetime.

Overview

• In the Zend API, a module is loaded into memory only once when the associated PHP process starts up. Each module recieves a call to the "module initialization" function specified in its zend_module structure as it is loaded.
• Whenever the associated PHP process starts to handle a request from its client - i.e. whenever the PHP interpreter is told to start working - each module receives a call to the "request initialization" function specified in its zend_module structure.
• Whenever the associated PHP process is done handling a request, each module receives a call to the "request termination" function specified in its zend_module structure.
• A given module is unloaded from memory when its associated PHP process is shut down in an orderly manner. The module receives a call to the "module termination" function specified in its zend_module structure at this time.