By far I am not an expert but that's pretty easy!
html:
<form action="path/to/filename.php" method="post">
<input type="text" name="nameyourposteddata" />
(and/or other form inputs/tag names incl types & names)
</form>
php:
$nameyourhandle=fopen("namenewfiletowrite.txt", "w");
fwrite($nameyourhandle, POST["nameyourposteddata"]);
(do the same for each additional tag, with proper post variables, and for strings of proper formatting characters--newlines, etc.)
fclose($namenewfiletowrite);
then close your php with the tag and follow it with the html you want to put to the browser.
Easy?
If you need more thorough help: www.w3schools.com/php/php_forms.asp
Hope this helps.
Edited by newessence, 03 April 2014 - 10:42 PM.