I don't understand how to add the Nocaptcha Recaptcha to my php site

I have a php-driven website running a script other than Word Press.  There is no available plug-in for it to add the NoCaptcha Recaptcha.  I am not a php programmer, but I can usually tweak php to make it work, after much trial and error.I'm stumped by Google's instructions, which only give instructions on how to add it to an html page. My site's index page is index.php, not index.html. I clicked the "php" link on the intro page and it goes to the github where there are numerous files with no explanation of where to put them or how to integrate.I found several sites that purport to explain how to add it to a php driven site, but they also rely on html for the page that holds the site key.  If it has to be an html page, what should it be named?  -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/P65DvS.