How to create a custom PHP page that have access to all variables and functions within the environment of our WordPress blog? The answer is very simple.
First create a page in your theme folder:
/wp-content/themes/your-theme-name/page.php
After that use this code in the top of your page
<?php define('WP_USE_THEMES', false); require('../../../wp-blog-header.php'); ?>
Now you can easly use all the functions specific to WordPress (primarily the loop) in your custom page.