First, let's find every PHP file where the application calls a mysql function: find . -name '*.php' -exec grep -Hil 'mysql_' {} \; -H with filename -i ignore case (because PHP is case-insensitive, MYSQL_ is possible but quite rare) -l list only the filename, with no context for the match Results in: ./FREDts/content/geshi/geshi/php-brief.php ./FREDts/content/geshi/geshi/php.php ./components/com_user/user.php ./installation/install2.php ./installation/install4.php ./installation/index.php ./modules/mod_stats.php ./administrator/components/com_checkin/admin.checkin.php ./administrator/components/com_admin/admin.admin.html.php ./includes/feedcreator.class.php ./includes/phpInputFilter/class.inputfilter.php ./includes/database.php ./includes/getids.php Hmm. FRED doesn't offer a clean separation of database functionality, either by database (everything is calling the %mysql_% functions directly inline) or by type of functionality (for example, there isn't a %*_db.php% file corresponding to each subdirectory). One way of proceeding would be to abstract the database functionality into a separate layer so that the correct database implementation can be loaded based on a configuration option.