Programming PHP

External Commands
PHP uses the default command shell of Windows for process manipulation. Only
rudimentary Unix shell redirections and pipes are available under Windows (e.g.,
separate redirection of standard output and standard error is not possible), and the
quoting rules are entirely different. The Windows shell does not glob (i.e., replace
wildcarded arguments with the list of files that match the wildcards). Whereas on
Unix you can say system("someprog php*.inc"), on Windows you must build the list
of filenames yourself using opendir( ) and readdir( ).
Common Platform-Specific Extensions
There are currently over 80 extensions for PHP, covering a wide range of services and
functionality. Only about half of these are available for both Windows and Unix
platforms. Only a handful of extensions, such as the COM, .NET, and IIS extensions,
are specific to Windows. If an extension you use in your scripts is not currently
available under Windows, you need to either port that extension or convert
your scripts to use an extension that is available under Windows.
If you use PHP as a web server plug-in (SAPI), the extensions must be thread-safe.
Some extensions depend on third-party libraries that may not be thread-safe, rendering
them incompatible with the SAPI plug-in.
Unfortunately, the level of thread safety in PHP extensions is poorly documented,
and it will require testing on your part to discover where you may run into difficulty.
Fortunately, the more popular an extension is, the greater chance there is of that
extension being available on Windows.
In some cases, some functions are not available under Windows even though the
module as a whole is. checkdnsrr( ), in the Networking module, is just one example
of this problem.
Windows PHP does not support signal handling, forking, or multithreaded scripts. A
Unix PHP script that uses these features cannot be ported to Windows. Instead, you
should rewrite the script to not take advantage of those features.
Interfacing with COM
COM allows you to control other Windows applications. You can send file data to
Excel, have it draw a graph, and export the graph as a GIF image. You could also use
Word to format the information you receive from a form and then print an invoice as
a record. After a brief introduction to COM terminology, this section shows you how
to interact with both Word and Excel.
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