like-function.php

<?php

add_action('init', 'j_set_like_cookie');
define('JEG_COOKIE_NAME', 'wp-jeg-setting');

add_action('wp_ajax_vote_post'          , 'j_ajax_vote_post');
add_action('wp_ajax_nopriv_vote_post'   , 'j_ajax_vote_post');

add_action('wp_ajax_total_vote'             , 'j_ajax_total_vote');
add_action('wp_ajax_nopriv_total_vote'      , 'j_ajax_total_vote');

function j_set_like_cookie() {
    if(!isset($_COOKIE[JEG_COOKIE_NAME])) {
        $cookieTimeout = j_get_option("cookie_timeout", time() + 24 * 60 * 60 * 30);
        setcookie(JEG_COOKIE_NAME, uniqid(), $cookieTimeout, '/');
    }
}

function j_get_like_count($postid) {
    global $wpdb;
    $themetable = $wpdb->prefix . JEG_SHORTNAME . '_post_like';

    $count = j_get_meta('post_initial_like', 0, $postid) + $wpdb->get_var("SELECT COUNT(id) FROM $themetable WHERE post_id = '$postid'");
    return $count;
}

function j_ajax_total_vote () {
    $total = j_get_like_count($_REQUEST['postid']);
    jsendResponse(array(
        total   => $total
    ));
}

function j_have_voted ($postid) {
    global $wpdb;
    $ip     = $_SERVER['REMOTE_ADDR'];
    if(isset($_COOKIE[JEG_COOKIE_NAME])) {
        $cookie = $_COOKIE[JEG_COOKIE_NAME];
    } else {
        $cookie = '';
    }
    $themetable = $wpdb->prefix . JEG_SHORTNAME . '_post_like';

    if(!empty($ip) && !empty($cookie)) {
        $vote = $wpdb->get_var("SELECT COUNT(id) FROM $themetable WHERE post_id = '$postid'" .
            " AND ip = '$ip'" .
            " AND cookie = '$cookie'");
        if($vote == 0) {
            return false;
        } else {
            return true;
        }
    } else {
        return NULL;
    }
}


function jeg_mysql_escape($inp) {
    if(is_array($inp))
        return array_map(__METHOD__, $inp);

    if(!empty($inp) && is_string($inp)) {
        return str_replace(array('\\', "\0", "\n", "\r", "'", '"', "\x1a"), array('\\\\', '\\0', '\\n', '\\r', "\\'", '\\"', '\\Z'), $inp);
    }

    return $inp;
}


function j_add_vote($postid) {
    global $wpdb;
    $ip     = $_SERVER['REMOTE_ADDR'];
    $cookie = jeg_mysql_escape($_COOKIE[JEG_COOKIE_NAME]);
    $themetable = $wpdb->prefix . JEG_SHORTNAME . '_post_like';

    if(!empty($ip) && !empty($cookie) && !empty($postid)) {

        if(j_have_voted($postid) === false) {
            $query = "INSERT INTO $themetable SET ";
                $query .= "post_id = '" . $postid . "', ";
                $query .= "date_time = '" . date('Y-m-d H:i:s') . "', ";
                $query .= "ip = '$ip', ";
                $query .= "cookie = '$cookie' ";

            $success = $wpdb->query($query);
            if($success) {
                return 3;
            } else {
                return 2;
            }
        } else {
            return 1;
        }

    } else {
        return 0;
    }
}

function j_ajax_vote_post() {
    $result = j_add_vote($_REQUEST['postid']);
    switch ($result) {
        case 0 :
            jsendResponse(array(
                'id'        => 0,
                'msg'       => j__('parameter_not_complete_lang')
            ));
            break;
        case 1 :
            jsendResponse(array(
                'id'        => 1,
                'msg'       => j__('have_voted_lang')
            ));
            break;
        case 2 :
            jsendResponse(array(
                'id'        => 2,
                'msg'       => j__('db_error_lang')
            ));
            break;
        case 3 :
            jsendResponse(array(
                'id'        => 3,
                'msg'       => j__('thanks_vote_lang'),
                'total'     => j_get_like_count($_REQUEST['postid'])
            ));
            break;
        default :
            break;
    }
}