After searching around for a code snippet that would do the trick when it comes to registering a user through Ninja Forms to no avail, I managed to put one together that works a treat.
All you need to do is change some of the IDs in the code to match your form details and then pop this into your theme’s functions.php file and you’ll be good to go.
You can even create multiple versions of this code snippet, just change up the name nf_create_user where it appears in the code.
UPDATE: 26th October 2016 – With Ninja Forms 3 there was a change to the form processing, check out the 2.x file below for registering users with old versions of Ninja Forms and the 3.x file below for registering with Ninja Forms 3 onwards.
If you’ve got any questions or comments on how this piece of code works, feel free to get in touch with me in the comments below!