Uploaded WP Files – Random Download?

I switched my hosts, and I imported the database from the old host and edited the config and such, and I uploaded all of the files that were in my public_html on my other host into my new one (all the files for WP) and now, whenever I try going to my website it downloads a file, why is this?! *It doesn’t load my site at all, all I can do is download that file. :blackhat:

Edit ; The file shows the following when opening the file on my PC ;

<?php
/**
 * Front to the WordPress application. This file doesn't do anything, but loads
 * wp-blog-header.php which does and tells WordPress to load the theme.
 *
 * @package WordPress
 */

/**
 * Tells WordPress to load the WordPress theme and output it.
 *
 * @var bool
 */
define('WP_USE_THEMES', true);

/** Loads the WordPress Environment and Template */
require( dirname( __FILE__ ) . '/wp-blog-header.php' );