Programming PHP

if (extension_loaded($module)) {
$str = $function($module);
} else {
$str = "Module $module is not compiled into PHP";
}
echo "$str\n";
?>
This code checks to see an if the extension is loaded, lists the functions provided by
the extension, and then calls the confirmation function if the extension was loaded.
This is good, but it doesn’t test whether the rot13( ) function works.
Modify the test script to look like this:
Run the test with:
% ~/php4/ext/rot13> php -q rot13.php
Enfzhf Rasmus
The test program encrypts “Rasmus”, then uses rot13( ) on the string again to
decrypt it. The -q option tells the command-line version of PHP to not display any
HTTP headers.
The config.m4 File
The config.m4 file contains the code that will go into the configure script. This
includes the switch that enables the extension (e.g., --enable-rot13 or --with-rot13),
the name of the shared library to build, code to search for prerequisite libraries, and
much more. The skeletal config.m4 file contains sample code for the various things
you might want to do, commented out.
There are conventions governing the configure switch to enable your extension. If
your extension does not rely on any external components, use --enable-foo. Ifit
does have some nonbundled dependencies, such as a library, use --with-foo.
Optionally, you can specify a base path using --with-foo=/some/path, which helps
configure find the dependencies.
PHP uses the grand unifying scheme of autoconf, automake, and libtool to build
extensions. These three tools, used together, can be extremely powerful, but they can
also be extremely frustrating. Getting this stuff right is a bit of a black art. When an
extension is part of the PHP source tree and you run the buildconf script in the top
directory of the tree, it scans through all its subdirectories looking for config.m4 files.
This is the Title of the Book, eMatter Edition
Copyright © 2002 O’Reilly & Associates, Inc. All rights reserved.
The config.m4 File | 327