<?php

/*
 * This is a rather simple and contrived example but it illustrates how this
 * function can be used to temporarily change the post context.
 */
$alt_post_content = override_post_context( 1234, function ( $post ) {
	ob_start();

	// Do whatever you need here. The $post variable, in this scope, is the
	// $post object we are currently working with.
	get_template_part('some/template');

	return ob_get_clean();
} );