以下是我以前使用过的函数：

function registration_form_wpa95139(){
    if (is_user_logged_in()) return;
    ?>
    <div class="Registration">
        <div id="register-form">
            <div class="title">
                <h1><?php _e(\'Register your Account\'); ?></h1>
                <span><?php _e(\'Sign Up with us and Enjoy!\'); ?></span>
            </div>
            <form action="<?php echo site_url(\'wp-login.php?action=register\', \'login_post\') ?>" method="post">
                <input type="text" name="user_login" value="Username" id="user_login" class="input" placeholder="Username" />
                <input type="text" name="user_email" value="E-Mail" id="user_email" class="input"  placeholder="E-Mail" />
                    <?php do_action(\'register_form\'); ?>
                    <input type="submit" value="<?php _e(\'Register\'); ?>" id="register" />
                <hr />
                <p class="statement"><?php _e(\'A password will be e-mailed to you.\'); ?></p>
            </form>
        </div>
    </div><!-- /Registration -->
    ?>
}

<?php registration_form_wpa95139() ;?>