registrations.php

<?php

require 'config.php';
require 'inc/connection.php';

function valid($data) {
    $valid = true;
    foreach ($data as $key => $value) {
        if ($value == '') {
            $valid = false;
            break;
        }
    }

    return $valid;
}

function already_registered($data) {
    global $db;
    $sql = 'SELECT * from users, events, registrations WHERE eventID = events.id && userID = users.id && users.token = :token  && eventID = :eventID';
    $q = $db->prepare($sql);
    $q->execute(array(':token' => $data['token'], ':eventID' => $data['eventID']));
    $result = $q->fetchAll();
    if (count($result)) {
        return true;
    } else {
        return false;
    }
}

function register($data) {
    global $db;

    $sql = 'SELECT id from `users` WHERE token = :token';
    $q = $db->prepare($sql);
    $q->execute(array(':token' => $data['token']));
    $result = $q->fetch();
    $userID = $result['id'];

    $sql = 'INSERT INTO `registrations` (eventID, userID, teamname, team) VALUES(:eventID, :userID, :teamname, :team)';
    $q = $db->prepare($sql);
    $q->execute(array(':eventID' => $data['eventID'],
                      ':userID' => $userID,
                      ':teamname' => $data['teamname'],
                      ':team' => $data['team'],
    ));
}

if (isset($_POST)) {
    if ($_POST['form'] == 'register') {
        $error = '';
        $data = array();
        if (valid($_POST)) {
            if (already_registered($_POST)) {
                $error = 'Already Registered';
            } else {
                register($_POST);
            }
        } else {
            $error = 'Please Fill The Form';
        }

        if ($error != '') {
            $data['success'] = false;
            $data['error'] = $error;
        } else {
            $data['success'] = true;
            $data['message'] = 'success';
        }

        echo json_encode($data);
    } elseif (isset($_POST['token'])) {
        global $db;
        $sql = $db->prepare('SELECT events.name, events.title, teamname from users, events, registrations WHERE eventID = events.id && userID = users.id && users.token = ?');
        $sql->execute(array($_POST['token']));
        $sql = $sql->fetchAll(PDO::FETCH_ASSOC);
        echo json_encode($sql);
    } else {
        echo 'error';
    }
} else {
    echo 'error';
}