Plugin Me Gusta

ajax-1.js

(function($) {

	var likeButton = $( "#like-button" );

	likeButton.on( "click", function(e) {
		e.preventDefault();

		var likes = likeButton.find('span').text(),
				postId = likeButton.data('post');

		$.ajax({
			type: 'post',
			dataType: 'json',
			url: a1_parameters.ajax_url,
			data: {
				action: 'a1_like_post',
				_ajax_nonce: a1_parameters.nonce,
				likes: likes,
				postId: postId
			},
			beforeSend: function(){
				console.log( 'Cargando...' );
			},
			success: function( response ){
				if( 'success' == response.type ){
					likeButton.find('span').text( response.likes );
				} else {
					console.log( 'Ha fallado.' );
				}
			}
		});

	});

}) ( jQuery );

ajax-1.php

<?php

/*
Plugin Name: Ajax 1
Description: Like en posts
*/

// Add like and counter link
add_filter( 'the_content', 'a1_add_like_link' );

function a1_add_like_link( $content ){

	if( !is_singular( 'post' ) ) return $content;

	$post_id = get_the_ID();

	$current_likes = get_post_meta( $post_id, 'a1_post_likes', true );

	$current_likes = ($current_likes == '') ? 0 : $current_likes;

	return $content . '<p><a href="#" id="like-button" data-post="' . $post_id . '"><span>' . $current_likes . '</span> Me gusta</a></p>';
}

// Enqueue scripts
add_action( 'wp_enqueue_scripts', 'a1_enqueue_scripts' );

function a1_enqueue_scripts(){
	if( is_singular( 'post' ) ):

		wp_enqueue_script( 
			'ajax-1',
			plugins_url( '/ajax-1.js', __FILE__ ),
			['jquery'],
			'1.0',
			true
		);

		wp_localize_script(
			'ajax-1',
			'a1_parameters',
			[
				'ajax_url'	=> admin_url( 'admin-ajax.php' ),
				'nonce'			=> wp_create_nonce( 'a1_nonce' )
			]
		);

	endif;
}

// Like a post
add_action( 'wp_ajax_a1_like_post', 'a1_like_post' );
add_action( 'wp_ajax_nopriv_a1_like_post', 'a1_like_post' );

function a1_like_post(){

	check_ajax_referer( 'a1_nonce' );
	$likes = intval( $_POST['likes'] ) + 1;
	$post_id = intval( $_POST['postId'] );

	$success = update_post_meta( $post_id, 'a1_post_likes', $likes );

	if( $success == true ):
		$response['likes'] = $likes;
		$response['type'] = 'success';
	else:
		$response['type'] = 'failure';
	endif;

	$response = json_encode( $response );

	echo $response;

	wp_die();
}