This extension is enabled by default. It may be
disabled by using the following option at compile time:
These functions are enabled by default, using the
bundled expat library. You can disable XML support with
–disable-xml . If you
compile PHP as a module for Apache 1.3.9 or later, PHP will
automatically use the bundled expat library from Apache. If you don’t want
to use the bundled expat library, configure PHP with –with-expat-dir=DIR , where DIR should
point to the base installation directory of expat.
The Windows version of PHP has built-in support
for this extension. You do not need to load any additional
extensions in order to use these functions.