Create your php file. Add your return email address. For the email to work, your email should have the same domain address as the hosting website where the php resides. This will authenticate you as a legit user. Most domains have email forwarding so you can forward to any 3rd party email providors (gmail, yahoo). Save your file as "feedback_form.php" (with all lower case)
Create your html file and reference your php file. Save your file as "feedback_form.html" (with all lower case)
Copy both html and php to your website's root folder, where your home page resides.
optional: Add conditionals and required feilds. add validators and spam filters to keep spammers from intercepting your email address for spamming purposes.