Users.php

<?php
function register_user($register_data) {
    array_walk($register_data, 'array_sanitize');
    $register_data['password'] = md5($register_data['data']);

    $fields = '`' . implode('`, `', array_keys($register_data)) . '`';
    $data = '\'' . implode('\', \'', $register_data) . '\'';

    mysql_query("INSERT INTO users ($fields) VALUES ($data)");
}

function user_count() {
    return mysql_result(mysql_query("SELECT COUNT(user_id) FROM users WHERE active = 1"), 0);
}


function user_data($user_id) {
    $data = array();
    $user_id = (int)$user_id;

    $func_num_args = func_num_args();
    $func_get_args = func_get_args();

    if ($func_num_args > 1) {
        unset($func_get_args[0]);

        $fields = '`' . implode('`, `', $func_get_args) . '`';
        $data = mysql_fetch_assoc(mysql_query("SELECT $fields FROM users WHERE user_id = $user_id"));

        return $data;
    }

}
function logged_in() {
    return (isset($_SESSION['user_id'])) ? true : false;
}

function user_exists($username) {
    $username = sanitize($username);
    $query = mysql_query("SELECT COUNT(user_id) FROM users WHERE username = '$username'");
    return (mysql_result($query, 0) == 1) ? true : false;
}
function email_exists($email) {
    $email = sanitize($email);
    $query = mysql_query("SELECT COUNT(user_id) FROM users WHERE email = '$email'");
    return (mysql_result($query, 0) == 1) ? true : false;
}
function user_active($username) {
    $username = sanitize($username);
    $query = mysql_query("SELECT COUNT(user_id) FROM users WHERE username = '$username' AND active = 1");
    return (mysql_result($query, 0) == 1) ? true : false;
}
function user_id_from_username($username) {
    $username = sanitize($username);
    return mysql_result(mysql_query("SELECT user_id FROM users WHERE username = '$username'"), 0, 'user_id');
}

function user_login($username, $password) {
        $user_id = user_id_from_username($username);
        $username = sanitize($username);
        $password = md5($password);

        return (mysql_result(mysql_query("SELECT COUNT(user_id) FROM users WHERE username = '$username' AND password = '$password'"), 0) == 1) ? $user_id : false;
}


?>