A simple WordPress plugin that generates QR codes in WordPress - just feed your data into an image URL and it'll generate QR code to embed anywhere you like.
Just clone this into your plugins folder, like so:
cd wp-content/plugins/
git clone https://github.com/wp-pure/qr
To embed a QR code in a confirmation email from any Gravity Form, paste the following into the 'Text' editor for that confirmation:
<img src="https://MYSITE.COM/wp-content/plugins/qr/generate.php?entry={form_id}::{entry_id}" />
Do remember to replace the MYSITE.COM part with your actual domain name, and everything will just work.
You can also use this to generate ANY QR code you like - just feed the content of that QR code into the data parameter of the URL, and it'll generate the QR code for you.
<img src="https://MYSITE.COM/wp-content/plugins/qr/generate.php?data=DATA" />
Developed with love by James Pederson.