Bootstrap 4 Form Generator

class Former{

    public $data = array();
    public $label = array();
    public $form = array();

    public $template = array(
        "label" => "<label class='col-sm-{div} col-form-label text-{align}'>{label}</label>",
        "input" => "<input type='{type}' class='form-control {class}' id='{id}' name='{name}' placeholder='{placeholder}' value='{value}'>",
        "textarea" => "<textarea class='form-control {class}' id='{id}' name='{name}' placeholder='{placeholder}'>{value}</textarea>",
        "select" => "<select class='form-control {class}' id='{id}' name='{name}'>{option}</select>",
        "option" => "<option value='{value}'>{option}</option>"
    );

    public static function run($config, $data){
        $result = "";
        $FORMER = new Former();
        $FORMER->data = $data;
        $form = json_decode($config);

        $label = array(
            "div" => $form->label_division,
            "row" => ($form->dom == "inline") ? "row" : "",
            "align" => ($form->dom == "inline") ? "right" : "left"
        );
        $FORMER->label = $label;

        foreach($form->form as $f){
            if($f->type != "hidden"){
                $FORMER->label['label'] = $f->label;
                $result .= "<div class='form-group " . $FORMER->label['row'] . "'>";
                $result .= $FORMER->add_label($FORMER->label);
            }

            if(empty($f->double)){
                $result .= "<div class='col'>";
                $FORMER->form = $f;
                $result .= $FORMER->switcher();
                $result .= "</div>";
            } else {
                foreach($f->double as $fd){
                    $result .= "<div class='col'>";
                    $FORMER->form = $fd;
                    $result .= $FORMER->switcher();
                    $result .= "</div>";
                }
            }

            if($f->type != "hidden"){
                $result .= "</div>";
            }
        }

        return $result;
    }

    public function switcher(){
        $result = "";
        switch($this->form->type){
            case "select":
                $result .= $this->add_select();
                break;
            case "radiobutton":
                break;
            case "textarea":
                $result .= $this->add_input("textarea");
                break;
            case "checkbox":
                break;
            default:
                $result .= $this->add_input();
                break;
        }

        $result = preg_replace("/\{\w*\}/", "", $result);
        return $result;
    }

    public function add_label($label){
        $template = $this->template['label'];
        foreach($label as $head => $value){
            $template = str_replace("{" . $head . "}", $value, $template);
        }
        return $template;
    }

    private function add_input($kind = ""){
        $template = $this->template[($kind == "") ? 'input' : 'textarea'];
        foreach($this->form as $index => $value){
            $template = str_replace("{" . $index . "}", $value, $template);
            if($index == "value"){
                if(substr($value,0,1) == "$"){
                    $template = str_replace($value, $this->data[substr($value,1)], $template);
                }
            }
        }
        return $template;
    }

    private function add_select(){
        $select_option = "";
        $select = $this->template['select'];
        $option = $this->template['option'];

          foreach($this->form as $index => $value){
            if($index == "option"){
                if(is_string($value)){
                    $func = substr($value,6);
                    foreach($func() as $op){
                        $select_option .= str_replace("{value}", $op->value, str_replace("{option}", $op->option, $option));
                    }
                } else {
                    foreach($value as $op => $o){
                        $select_option .= str_replace("{value}", $op, str_replace("{option}", $o, $option));
                    }
                }
            } else {
                $select = str_replace("{" . $index . "}", $value, $select);
            }
        }

        return str_replace("option", $select_option, $select);
    }

}