From PHP 5.4.5, COM and DOTNET is no longer built into the php core.you have to add COM support in php.ini:
Otherwise you will see this in your error log:
Fatal error: Class \'COM\' not found
The extension is included with php 5.4.5 for Windows.
As of PHP 5.3.15 / 5.4.5, this extension requires php_com_dotnet.dll to be enabled inside of php.ini in order to use these functions. Previous versions of PHP enabled these extensions by default.
You are responsible for installing support for the various COM objects that you intend to use (such as MS Word); we don't and can't bundle all of those with PHP.
As of 5.3.15 (if you are still on 5.3 branch) you have to add extension=php_com_dotnet.dll line into your php.ini to have COM, DOTNET, VARIANT and similar classes available and working.
From PHP Change log:
Fixed bug #62146 com_dotnet cannot be built shared
Because of this, the official PHP builds for Windows are now built with "--enable-com-dotnet=shared" option, which means no COM/DOTNET support by default.
Some of my projects that I currently maintain use adodb library which uses VARIANT class and fails to work without it.