Display Popular Posts by Views in WordPress without a Plugin

popular-post-data-setup.php

<?php
/**
 * POPULAR POSTS DATA SETUP
 * It will set 'post_views_count' meta data to count popular posts
*/
function ic_set_post_views($postID) {
    $count_key = 'post_views_count';
    $count = get_post_meta($postID, $count_key, true);
    if($count==''){
        $count = 0;
        delete_post_meta($postID, $count_key);
        add_post_meta($postID, $count_key, '0');
    }else{
        $count++;
        update_post_meta($postID, $count_key, $count);
    }
}
//To keep the count accurate, lets get rid of prefetching
remove_action( 'wp_head', 'adjacent_posts_rel_link_wp_head', 10, 0);

function ic_track_post_views ($post_id) {
    if ( ! is_singular('apps') ) return;
    if ( empty ( $post_id) ) {
        global $post;
        $post_id = $post->ID;    
    }
    ic_set_post_views($post_id);
}
add_action( 'wp_head', 'ic_track_post_views');

popular-posts-query.php

<?php
// QUERY ARGUMENTS
$args = array(
    'post_type' => 'apps',
    'posts_per_page'  => -1,
);

$args['meta_key']   = 'post_views_count';
$args['orderby']    = 'meta_value_num';
$args['order']      = 'DESC';

// The Query
$the_query = new WP_Query( $args );

// The Loop
if ( $the_query->have_posts() ) {
	echo '<ul>';
	while ( $the_query->have_posts() ) {
		$the_query->the_post();
		echo '<li>' . get_the_title() . '</li>';
	}
	echo '</ul>';
	/* Restore original Post Data */
	wp_reset_postdata();
} else {
	// no posts found
}