WC_Settings_API::validate_textarea_field PHP Method

    public function validate_textarea_field($key, $value)
    {
        $value = is_null($value) ? '' : $value;
        return wp_kses(trim(stripslashes($value)), array_merge(array('iframe' => array('src' => true, 'style' => true, 'id' => true, 'class' => true)), wp_kses_allowed_html('post')));
    }