finlabsindia/wp-content/plugins/ninja-forms/includes/Fields/ListMultiSelect.php

<?php if ( ! defined( 'ABSPATH' ) ) exit;

/**
 * Class NF_Fields_MultiselectList
 */
class NF_Fields_ListMultiselect extends NF_Abstracts_List
{
    protected $_name = 'listmultiselect';

    protected $_type = 'listmultiselect';

    protected $_nicename = 'Mulit-Select';

    protected $_section = 'common';

    protected $_templates = 'listselect';

    protected $_old_classname = 'list-multiselect';

    protected $_settings = array( 'multi_size' );

    public function __construct()
    {
        parent::__construct();

        $this->_nicename = __( 'Multi-Select', 'ninja-forms' );

        add_filter( 'ninja_forms_merge_tag_calc_value_' . $this->_type, array( $this, 'get_calc_value' ), 10, 2 );
    }

    public function admin_form_element( $id, $value )
    {
        $field = Ninja_Forms()->form()->get_field( $id );

        $options = '';
        foreach( $field->get_setting( 'options' ) as $option ){
            $selected = ( is_array( $value ) && in_array( $option[ 'value' ], $value ) ) ? "selected" : '';
            $options .= "<option value='{$option[ 'value' ]}' $selected>{$option[ 'label' ]}</option>";
        }

        return "<select class='widefat' name='fields[$id][]' id='' multiple>$options</select>";
    }

    public function get_calc_value( $value, $field )
    {
        $selected = explode( ',', $value );
        $value = 0;
        if( isset( $field[ 'options' ] ) ) {
            foreach ($field['options'] as $option ) {
                if( ! isset( $option[ 'value' ] ) || ! in_array( $option[ 'value' ], $selected )  || ! isset( $option[ 'calc' ] ) ) continue;
                $value +=  $option[ 'calc' ];
            }
        }
        return $value;
    }
}