$(document).ready(function(event) {

    $('body').on('click', '.firstadd', function(event) {

        var link = $(this);

        var first = $(this).attr('data-first');
        successfunc();
        $.ajax({
            url: 'first.php',
            method: 'POST',
            data: {"first" : first}
        })
    });
});


//php

session_start();
$first = $_POST['first'];

if (empty($_SESSION['rating'])) {
    $_SESSION['rating'] = [];
};

if (!in_array($first, $_SESSION['rating'])) {

    $_SESSION['rating'][] = $first;
    $success = 1;
};