How to create multi-select type input in magento 2 custom form?

How to create multi-select type input in magento 2 custom form? – Usually in our custom module we have custom form to enter data. We use text box, Select, Text-area etc in our forms. Recently i faced an issue while creating the form with multi-select input type. So i will write this article to explain how to create a multi-select type input type and save the data.

Create the field – Main.php ( app/code/Ayakil/FreeGift/Block/Adminhtml/Freegifts/Edit/Tab/Main.php )

//----------
 $fieldset->addField(
            'elegible_products',
            'multiselect',
            [
                'label' => __('Products'),
                'title' => __('Products'),
                'name' => 'elegible_products',
                'required' => true,
                'values' => \Ayakil\FreeGift\Block\Adminhtml\Freegifts\Grid::getValueArray4(),
                'disabled' => $isElementDisabled
            ]

        );
//----------

Create the getOptionArray4 function – Grid.php ( app/code/Ayakil/FreeGift/Block/Adminhtml/Freegifts/Grid.php )

//------------
static public function getOptionArray4()
{
        $data_array=array();
        $data_array[0]='Product 1';
        $data_array[1]='Product 2';
        $data_array[2]='Product 3';
        return($data_array);

}

static public function getValueArray4()
{
     $data_array=array();
foreach(\Ayakil\FreeGift\Block\Adminhtml\Freegifts\Grid::getOptionArray4() as $k=>$v){
               $data_array[]=array('value'=>$k,'label'=>$v);
		}
      return($data_array);
}
//------------

With these after i run the setup:upgrade. If i tried to add the data, i am getting an error like below.

{“0″:”Notice: Array to string conversion in /home/muja/www/ayakil-greens/vendor/magento/framework/DB/Adapter/Pdo/Mysql.php on line 3105″,”1”

For this we want to edit the save controller( app/code/Ayakil/FreeGift/Controller/Adminhtml/freegifts/Save.php ) with following code. Want to implode the values and set the data to save.

public function execute()
    {
        $data = $this->getRequest()->getPostValue();

        $data['elegible_products'] = implode(',',$data['elegible_products']);
    //---------- Other codes going below
}

That’s it , many articles covered how to create a multi-select but i thought to include the error while saving the form and solution with this article,Hope this may help some one’s time in future.

That’s it. Have a nice day.Enjoy coding , Learn , Experience , Teach and Help.