Scanning a QR code into a browser text input?
It is possible if you let's say generate a QR-code that leads to 

http://www.yourdomain.com/yourpage.php?inputtext=1234

When the user scans the QR-code he will be sent to http://www.yourdomain.com/yourpage.php and then your page takes the value of inputtext which is 1234 and puts in the input field of your choice.