use mu-plugins for adding custom functionality to your wordpress site

You have created theme, and editing the theme's functions php ...   By the output templates in the theme is defined, all your changes will be lost the time you're updating the theme. functions php is where functions used.   Theme modifies the way the site is displayed, without modifying the underlying software..   Consider this Is this functionality you want to keep if you change the theme.   Plugins are ways to extend and add to the functionality that already exists WordPress..   the in these mu-plugins will be loaded on all the in your installation.   you better make option to whether your mu-plugin should run any code or make it regular plugin instead..   then creating mu-plugin might be very good choice for you..   To add mu-plugin, all you have to do is to drop PHP file into the wp-content mu-plugins directory.   To use this, just drop the code into PHP file, e.g twitter-follow php in the mu-plugins folder < php add filter { return $content.   Read more