使用jQery填充select字段的方式，当您可以使用filter并使用PHP钩住表单时，例如：

 //1. Add a new form element...
add_action(\'register_form\',\'_register_form_wpa103118\');
function _register_form_wpa103118 (){
    $name_of_select = ( isset( $_POST[\'name_of_select\'] ) ) ? $_POST[\'name_of_select\']: \'\';
    $options = array(
        \'Medicine\' => \'Medicine\',
        \'Option2\' => \'Option2\',
    );
    ?>
    <p>
        <label for="name_of_select"><?php _e(\'First Name\',\'mydomain\') ?><br />
            <select name="name_of_select">
                <?php
                foreach ($options as $key => $value) {
                    $selected = ($value == $name_of_select)? \' selected="selected"\': \'\';
                    echo \'<option\'.$selected.\' value="\'.$key.\'">\'.$value.\'</option>\';
                }
                ?>
            </select>
    </p>
    <?php
}

//2. Add validation. In this case, we make sure first_name is required.
add_filter(\'registration_errors\', \'_registration_errors_wpa103118\', 10, 3);
function _registration_errors_wpa103118 ($errors, $sanitized_user_login, $user_email) {
    if ( empty( $_POST[\'name_of_select\'] ) )
        $errors->add( \'name_of_select\', __(\'<strong>ERROR</strong>: You must select ....\') );

    return $errors;
}

//3. Finally, save our extra registration user meta. or do whatever you want with it.
add_action(\'user_register\', \'_user_register_wpa103118\');
function _user_register_wpa103118 ($user_id) {
    if ( isset( $_POST[\'name_of_select\'] ) )
        update_user_meta($user_id, \'name_of_select\', $_POST[\'name_of_select\']);
}