loop.php

<?php
namespace gmazzap;

/**
 * @param callable $looper Callback that receives post object, post index and current WP_Query.
 *                         It is possible to use any template tags inside the callback.
 * @param array    $args   Array of WP_Query arguments. Optional, when not provided, main query will be used.
 */
function loop(callable $looper, array $args = null) {

    $query = $args === null ? $GLOBALS['wp_query'] : new \WP_Query($args);

    array_walk($query->posts, function(\WP_Post $post, int $index, \WP_Query $wp_query) use ($looper) {

        $GLOBALS['post'] = $post;
        $wp_query->the_post();
        $looper($post, $index, $wp_query);
        $wp_query->have_posts(); // this will fire 'loop_end' when needed
    }, $query);

    $args === null or wp_reset_postdata();
}

Example with main query:

gmazzap\loop(function(\WP_Post $post, int $post_index, \WP_Query $wp_query) {
    ?>
	<div id="post-<?= $post->ID ?>" <?php post_class($post_index %2 === 0 ? 'even' : 'odd', $post->ID) ?>>
		<h2 class="title"><?php the_title() ?></h2>
		<div><?php the_content() ?></div>
	</div>
    <?php
});

Example with custom query:

gmazzap\loop(function(\WP_Post $post, int $post_index, \WP_Query $wp_query) {
    ?>
	<div id="post-<?= $post->ID ?>" <?php post_class($post_index %2 === 0 ? 'even' : 'odd', $post->ID) ?>>
		<h2 class="title"><?php the_title() ?></h2>
		<div><?php the_content() ?></div>
	</div>
    <?php
}, ['post_type' => 'product', 'posts_per_page' => 10]);