Does the file extension matter to search engines or is it all code based? I ask because I have one page that was made in HTML put renamed it to php.
It doesn't matter at all what file extension is used. Now, with that said if SE's indexed a html version and you changed it to php, then their going to have to re-cache the page because it's seen as a different web page.
You can easily make your .html files run php code by adding an apache handler. You can check with your hosting company on how to do this. If they use Cpanel, you can go into your "mime types" and added a user defined handler. Ex. Mimetype = application/x-httpd-php extension = .html
it doesn't matter at all whether you use HTML or PHP for a search engine, it's the same. The only convinience about php is that many search engines index it very fast isnt it ? I always see a php website get indexed more faster than a HTML one.
1st phrase - true 2nd phrase - false the only fact that you have to think of is that most SE don't like URLs with more than 2 parametes. so if you have: index.php?id=10&product=cars&username=john SE won't like it and will rate it not very well. so you should use HTACCESS rewriting, which is not very easy, but it very powerfull. you chose your own encoding, something like this one from above for example: view-products-cars-item-10-seller-john.html good luck.
I agree with adolix about the "falseness" of the second phrase. I have made a one-year long test about Google's preferences aconcerning the file extensions for pages, and it doesn't seem to make a big difference. Yet in my test(s), the asp extension seems a little unfavored. .php and .html (or .htm) were about the same.