Simple Heart Extenstion for WordPress Posts

functions.php

<?php
/**
* Get Ip function 
*/

function get_current_user_ip() {
	if (!empty($_SERVER['HTTP_CLIENT_IP'])) :
	    $ip = $_SERVER['HTTP_CLIENT_IP'];
	elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) :
	    $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
	else :
	    $ip = $_SERVER['REMOTE_ADDR'];
	endif;
	return $ip;
}
// ajax Callback
add_action('wp_ajax_heart_it', 'heart_it', 0);
add_action('wp_ajax_nopriv_heart_it', 'heart_it');

function heart_it() {
	$user_ip_address = get_current_user_ip();
	$user_unique_name = str_replace('.', '_', $user_ip_address);
	$post_id = $_POST['post_id'];
	$posts_liked_by_current_user = get_option('liked_by_'.$user_unique_name);
	$post_like_count = get_post_meta($post_id, 'like_count', true);
	if( empty($posts_liked_by_current_user) ) :
		add_option('liked_by_'.$user_unique_name, array($post_id), false);
		$post_like_count++;
		update_post_meta($post_id, 'like_count', $post_like_count);
		$message = 'You have liked this post';
	else :
		if( in_array($post_id, $posts_liked_by_current_user) ) :
			$message = 'liked';
		else : 
			$post_like_count++;
			array_push($posts_liked_by_current_user, $post_id);
			update_option('liked_by_'.$user_unique_name, $posts_liked_by_current_user);
			update_post_meta($post_id, 'like_count', $post_like_count);
			$message = 'You have liked this post';
		endif; //in_array
	endif; //is liked posts empty
	$message_return = array('message'=>$message, 'like_count'=>$post_like_count);
	$message_json = json_encode($message_return);
	echo $message_json;
	die;
}

single.php

<?php
while(have_posts()): the_post();
    the_title();
    echo '<div class="like" data-id="'.$post->ID.'" user-id="'.get_current_user_id().'">Like</div>';
endwhile;
<script>
jQuery('.like').on('click', function() {
	var postID = jQuery(this).attr('data-id');
	var clickedThis = jQuery(this).parent().children('span.like').children().children('span');
	jQuery.ajax({
		type: 'POST',
		url: ajaxUrl,
		data: {
			action: "heart_it",
			post_id: postID,
		},
		success: function(result) {
			var responseJSON = jQuery.parseJSON(result);
			console.log(responseJSON.message);
			if( responseJSON.message != 'liked' ) {
				clickedThis.text(responseJSON.like_count);
			}
		}
	});
				
});
</script>