Craig Buckler has added a new post to the SitePoint PHP blog today that looks at some of the PHP configuration options and how you can change them from two different places (besides the php.ini file).
Configuring PHP is easy. You can change almost any aspect of the interpreter within the php.ini configuration file, e.g. modify error handling, increase memory usage, etc. Unfortunately, problems can occur when you move your application to a live hosting environment or are distributing the code to customers. ISPs usually lock down the php.ini configuration file - especially on shared hosting. This could cause your application to fail.
If you're lucky enough to be able to use htaccess files, his first method will work for you - using the "php_flag" or "php_value" directives to change settings for your entire application. The other option is more on an as needed basis - using the ini_set method to change configuration options. Be careful, though, only some configuration options can be changed using these methods. Some still require changes to the php.ini and a restart of the web server.