COM is a technology which allows the reuse of code written in any language (by any language) using a standard calling convention and hiding behind APIs the implementation details such as what machine the Component is stored on and the executable which houses it. It can be thought of as a super Remote Procedure Call (RPC) mechanism with some basic object roots. It separates implementation from interface.
COM encourages versioning, separation of implementation from interface and hiding the implementation details such as executable location and the language it was written in.
There is no installation needed to use these functions; they are part of the PHP core.
The windows version of PHP has built in support for this extension. You do not need to load any additional extension in order to use these functions.
The behaviour of these functions is affected by settings in php.ini.
Table 1. Com configuration options
The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.