post-like.php

<?php
/*
Name:  WordPress Post Like System
Description:  A simple and efficient post like system for WordPress.
Version:      0.1
Author:       Jon Masterson
Author URI:   http://jonmasterson.com/
*/
 
/**
 * (1) Enqueue scripts for like system
 */
function like_scripts() {
	wp_enqueue_script( 'like_post', get_template_directory_uri().'/js/post-like.js', array('jquery'), '1.0', 1 );
	wp_localize_script( 'like_post', 'ajax_var', array(
		'url' => admin_url( 'admin-ajax.php' ),
		'nonce' => wp_create_nonce( 'ajax-nonce' )
		)
	);
}
add_action( 'init', 'like_scripts' );

/**
 * (2) Add Fontawesome Icons
 */
function enqueue_icons () {
	wp_register_style( 'icon-style', 'http://netdna.bootstrapcdn.com/font-awesome/4.0.0/css/font-awesome.css' );
    wp_enqueue_style( 'icon-style' );
}
add_action( 'wp_enqueue_scripts', 'enqueue_icons' );

/**
 * (3) Save like data
 */
add_action( 'wp_ajax_nopriv_post-like', 'post_like' );
add_action( 'wp_ajax_post-like', 'post_like' );
function post_like() {
	$nonce = $_POST['nonce'];
    if ( ! wp_verify_nonce( $nonce, 'ajax-nonce' ) )
        die ( 'Nope!' );
	
	if ( isset( $_POST['post_like'] ) ) {
	
		$post_id = $_POST['post_id']; // post id
		$post_like_count = get_post_meta( $post_id, "_post_like_count", true ); // post like count
		
		if ( is_user_logged_in() ) { // user is logged in
			global $current_user;
			$user_id = $current_user->ID; // current user
			$meta_POSTS = get_user_meta( $user_id, "_liked_posts" ); // post ids from user meta
			$meta_USERS = get_post_meta( $post_id, "_user_liked" ); // user ids from post meta
			$liked_POSTS = ""; // setup array variable
			$liked_USERS = ""; // setup array variable
			
			if ( count( $meta_POSTS ) != 0 ) { // meta exists, set up values
				$liked_POSTS = $meta_POSTS[0];
			}
			
			if ( !is_array( $liked_POSTS ) ) // make array just in case
				$liked_POSTS = array();
				
			if ( count( $meta_USERS ) != 0 ) { // meta exists, set up values
				$liked_USERS = $meta_USERS[0];
			}		

			if ( !is_array( $liked_USERS ) ) // make array just in case
				$liked_USERS = array();
				
			$liked_POSTS['post-'.$post_id] = $post_id; // Add post id to user meta array
			$liked_USERS['user-'.$user_id] = $user_id; // add user id to post meta array
			$user_likes = count( $liked_POSTS ); // count user likes
	
			if ( !AlreadyLiked( $post_id ) ) { // like the post
				update_post_meta( $post_id, "_user_liked", $liked_USERS ); // Add user ID to post meta
				update_post_meta( $post_id, "_post_like_count", ++$post_like_count ); // +1 count post meta
				update_user_meta( $user_id, "_liked_posts", $liked_POSTS ); // Add post ID to user meta
				update_user_meta( $user_id, "_user_like_count", $user_likes ); // +1 count user meta
				echo $post_like_count; // update count on front end
				
			} else { // unlike the post
				$pid_key = array_search( $post_id, $liked_POSTS ); // find the key
				$uid_key = array_search( $user_id, $liked_USERS ); // find the key
				unset( $liked_POSTS[$pid_key] ); // remove from array
				unset( $liked_USERS[$uid_key] ); // remove from array
				$user_likes = count( $liked_POSTS ); // recount user likes
				update_post_meta( $post_id, "_user_liked", $liked_USERS ); // Remove user ID from post meta
				update_post_meta($post_id, "_post_like_count", --$post_like_count ); // -1 count post meta
				update_user_meta( $user_id, "_liked_posts", $liked_POSTS ); // Remove post ID from user meta			
				update_user_meta( $user_id, "_user_like_count", $user_likes ); // -1 count user meta
				echo "already".$post_like_count; // update count on front end
				
			}
			
		} else { // user is not logged in (anonymous)
			$ip = $_SERVER['REMOTE_ADDR']; // user IP address
			$meta_IPS = get_post_meta( $post_id, "_user_IP" ); // stored IP addresses
			$liked_IPS = ""; // set up array variable
			
			if ( count( $meta_IPS ) != 0 ) { // meta exists, set up values
				$liked_IPS = $meta_IPS[0];
			}
	
			if ( !is_array( $liked_IPS ) ) // make array just in case
				$liked_IPS = array();
				
			if ( !in_array( $ip, $liked_IPS ) ) // if IP not in array
				$liked_IPS['ip-'.$ip] = $ip; // add IP to array
			
			if ( !AlreadyLiked( $post_id ) ) { // like the post
			
				update_post_meta( $post_id, "_user_IP", $liked_IPS ); // Add user IP to post meta
				update_post_meta( $post_id, "_post_like_count", ++$post_like_count ); // +1 count post meta
				echo $post_like_count; // update count on front end
				
			} else { // unlike the post
			
				$ip_key = array_search( $ip, $liked_IPS ); // find the key
				unset( $liked_IPS[$ip_key] ); // remove from array
				update_post_meta( $post_id, "_user_IP", $liked_IPS ); // Remove user IP from post meta
				update_post_meta( $post_id, "_post_like_count", --$post_like_count ); // -1 count post meta
				echo "already".$post_like_count; // update count on front end
				
			}
		}
	}
	
	exit;
}

/**
 * (4) Test if user already liked post
 */
function AlreadyLiked( $post_id ) { // test if user liked before
	
	if ( is_user_logged_in() ) { // user is logged in
		global $current_user;
		$user_id = $current_user->ID; // current user
		$meta_USERS = get_post_meta( $post_id, "_user_liked" ); // user ids from post meta
		$liked_USERS = ""; // set up array variable
		
		if ( count( $meta_USERS ) != 0 ) { // meta exists, set up values
			$liked_USERS = $meta_USERS[0];
		}
		
		if( !is_array( $liked_USERS ) ) // make array just in case
			$liked_USERS = array();
			
		if ( in_array( $user_id, $liked_USERS ) ) { // True if User ID in array
			return true;
		}
		return false;
		
	} else { // user is anonymous, use IP address for voting
	
$meta_IPS = get_post_meta($post_id, "_user_IP"); // get previously voted IP address
$ip = $_SERVER["REMOTE_ADDR"]; // Retrieve current user IP
$liked_IPS = ""; // set up array variable

if ( count( $meta_IPS ) != 0 ) { // meta exists, set up values
	$liked_IPS = $meta_IPS[0];
}

if ( !is_array( $liked_IPS ) ) // make array just in case
	$liked_IPS = array();

if ( in_array( $ip, $liked_IPS ) ) { // True is IP in array
	return true;
}
return false;
	}
	
}

/**
 * (5) Front end button
 */
function getPostLikeLink( $post_id ) {
	$theme_object = wp_get_theme();
	$themename = esc_attr( $theme_object->Name ); // the theme name
$like_count = get_post_meta( $post_id, "_post_like_count", true ); // get post likes
if ( ( !$like_count ) || ( $like_count && $like_count == "0" ) ) { // no votes, set up empty variable
	$likes = 'Like';
} elseif ( $like_count && $like_count != "0" ) { // there are votes!
	$likes = esc_attr( $like_count );
}
	$output = '<span class="post-like">';
	$output .= '<a href="#" data-post_id="'.$post_id.'">';
	if ( AlreadyLiked( $post_id ) ) { // already liked, set up unlike addon
		$output .= '<span class="unliker"><i class="fa fa-times-circle"></i></span><span class="like prevliked"><i class="fa fa-heart"></i></span>';
		$output .= ' <span class="count alreadyliked">'.$likes.'</span></a></span>&nbsp; ';
	} else { // normal like button
		$output .= '<span class="unliker"></span><span class="like"><i class="fa fa-heart"></i></span>';
		$output .= ' <span class="count">'.$likes.'</span></a></span>&nbsp; ';
	}
	return $output;
}

/**
 * (6) Retrieve User Likes and Show on Profile
 */
add_action( 'show_user_profile', 'show_user_likes' );
add_action( 'edit_user_profile', 'show_user_likes' );
function show_user_likes( $user ) { ?>        
    <table class="form-table">
        <tr>
			<th><label for="user_likes"><?php _e( 'You Like:' ); ?></label></th>
			<td>
            <?php global $current_user;
			$user_likes = get_user_meta( $user->ID, "_liked_posts");
			if ( $user_likes && count( $user_likes ) > 0 ) {
				$the_likes = $user_likes[0];
			} else {
				$the_likes = '';
			}
			
			if ( !is_array( $the_likes ) )
			$the_likes = array();
			$count = count($the_likes); $i=0;
			if ( $count > 0 ) {
				$like_list = '';
				echo '<p>';
				foreach ( $the_likes as $the_like ) {
					$i++;
					$like_list .= '<a href="' . esc_url( get_permalink( $the_like ) ) . '" title="' . esc_attr( get_the_title( $the_like ) ) . '">' . get_the_title( $the_like ) . '</a>';
					if ($count != $i) $like_list .= ' &middot; ';
					else $like_list .= '</p>';
				}
				echo $like_list;
			} else {
				echo '<p>You don\'t like anything yet.</p>';
			} ?>
            </td>
		</tr>
    </table>
<?php }