WordPress Post Views Counter Without Any Plugin

function.php

<?php
function getPostViews($postID){
    $count_key = 'post_views_count';
    $count = get_post_meta($postID, $count_key, true);
    if($count==''){
        delete_post_meta($postID, $count_key);
        add_post_meta($postID, $count_key, '0');
        return "0 View";
    }
    return $count.' Views';
}
function setPostViews($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);
    }
}
// Remove issues with prefetching adding extra views
remove_action( 'wp_head', 'adjacent_posts_rel_link_wp_head', 10, 0);
?>

index.php

// Use the following line of code where you want to display the view number inside the loop.
// It will get the post view number from the last step where you call the set function to track the post views.
<?php 
if ( have_posts() ) {
	while ( have_posts() ) {
		the_post(); 
		//
		echo getPostViews(get_the_ID());
		//
	} // end while
} // end if
?>

single.php

<?php setPostViews(get_the_ID()); ?>