Hi I'd like to create a totally custom page in wordpress where I'd add a lot of php code so I would prefer not to create it as a wordpress 'Page', but as a file 'filename.php' in my theme directory. Of course in that page I need to include wp functions and stuff and I plan to do it with require_once("../../../../wp-load.php");.
My problem is, how do I set the header info for a custom page like that (title, meta description etc..) and how do I add a rewrite rule to make it reachable like "website.dom/pagename". Thanks in advance for any answer, and even if you tell me that the best way is to use wordpress default "Add New Page", I'd prefer not to use any script to insert php code in the page, thanks.
WordPress has built in functionality to look for custom pages, and does so every time you open up a page. To have WordPress find it you could for instance name the file page-{id}.php or page-{slug}.php and place it in your theme folder. So if the name of your page i "about" - which you create as you usually would, using the admin section in WordPress - you name your file "page-about.php". WordPress will then automatically load it.
To load the title of your page, use get_header( 'about' ); (Although, that's part of the header).
A good way to start would be to locate page.php, holding the default template, copy it and rename it as explained above. Then edit it in any way you want. You'll find a good guide here.
I suggest you create a WP page, and set it to use a custom template. Then, add your custom scripts to the template.