The behaviour of these functions is affected by settings in php.ini.
Here's a short explanation of the configuration directives.
When this is turned on, PHP will be allowed to operate as a D-COM (Distributed COM) client and will allow the PHP script to instantiate COM objects on a remote server.
When this is turned on, PHP will attempt to register constants from the typelibrary of COM objects that it instantiates, if those objects implement the interfaces required to obtain that information. The case sensitivity of the constants it registers is controlled by the configuration directive.
When this is turned on, any problems with loading a typelibrary during object instantiation will be reported using the PHP error mechanism. The default is off, which does not emit any indication if there was an error finding or loading the type library.
It controls the default character set code-page to use when passing
strings to and from COM objects. If set to an empty string, PHP will
assume that you want
CP_ACP, which is the default
system ANSI code page.
If the text in your scripts is encoded using a different encoding/character set by default, setting this directive will save you from having to pass the code page as a parameter to the com class constructor. Please note that by using this directive (as with any PHP configuration directive), your PHP script becomes less portable; you should use the COM constructor parameter whenever possible.
When set, this should hold the path to a file that contains a list of typelibraries that should be loaded on startup. Each line of the file will be treated as the type library name and loaded as though you had called com_load_typelib(). The constants will be registered persistently, so that the library only needs to be loaded once. If a type library name ends with the string #cis or #case_insensitive, then the constants from that library will be registered case insensitively.