It’s not often that a WordPress developer doesn’t modify the functions.php file within a theme they’re developing.
Why? Because functions.php gives you the power to control functionality specific to the theme. With some simple code inclusions and/or modifications, you can override existing website functionality and execute multiple functions in an efficient manner, instead of using potentially bulky and insecure plugins to achieve the same thing.
Although adding a few plugins can get the job done, learning the following ways to change WordPress websites through the functions.php file – located in your theme’s folder – is rather quick and easy.
The functions.php file basically acts like a WordPress plugin.
You can add code to call functions and change features and functionality on your client sites. In short, you can add as many functions to this file as you like, whereas plugins typically focus on one task, and you have to install a bunch of them to cover different areas.
If you don’t currently have a functions file for a theme, just create a file called functions.php and place it in the /wp-content/themes/yourthemename/ subdirectory. If you do have a functions.php file, or you want to figure out if your client sites have them, use an FTP client (such as FileZilla) to navigate to the /wp-content/themes/yourthemename/ subdirectory and look for the file.