Some PHP scripts may require settings different from the defaults configured in the server's php.ini file. You can change many of these settings by using php_value and php_flag directives in the .htaccess file in your web site's root folder.
Here are a few example settings:
(do not just add these, only change what is required by your scripts/website coding)
php_value include_path ".:/usr/local/lib/php"
php_flag display_errors Off
php_value post_max_size 15M
php_value upload_max_filesize 15M
Some notes from the PHP.net documentation on post_max_size and upload_max_filesize:
post_max_size sets the maximum size of post data allowed. This setting also affects file upload. To upload large files, this value must be larger than upload_max_filesize. Generally speaking, memory_limit should be larger than post_max_size.