[fw-general] Zend_Form_Element_Submit class attribute

[Kostyantyn Shakhov]

How to add a 'class' attribute to Zend_Form_Element_Submit element? It
doesn’t recognize it whatever way I tried:

        $this->addElement(
            'Submit',
            'btn_search',
            array(
                'label' => 'Search',
                'decorators' => $this->buttonDecorators,
                ‘class’ => ‘class_name’
            )
        );

or
      $this->getElement(‘btn_search’)->setAttrib('class', 'class_name');