sample.php

<?php
$query_args = array(
	'foo' => 'bar',
	'apple' => 'orange',
	'posts_per_page' => 50,
	'offset' => 0,
);
$some_posts = new WP_Query( $query_args );
while ( $some_posts->have_posts() ) {
	/*
	 * Do some stuff here
	 */
	// Get more posts
	$query_args['offset'] = $query_args['offset'] + $query_args['posts_per_page'];
	$some_posts = new WP_Query( $query_args );
}