Select with Select2 script

PHP

Select with select2 script

Demo

array(
  'id'         => 'unique_option_504',
  'type'       => 'select',
  'title'      => 'Select Field',
  'options'    => array(
    'green'    => 'Green',
    'blue'     => 'Blue',
    'yellow'   => 'Yellow',
  ),
  'class'      => 'chosen',
),

PHP

Multiple Select with select2 script

array(
  'id'            => 'unique_option_505',
  'type'          => 'select',
  'title'         => 'Select Field',
  'options'       => array(
    'green'       => 'Green',
    'blue'        => 'Blue',
    'yellow'      => 'Yellow',
  ),
  'class'         => 'chosen',
  'attributes'    => array(
    'placeholder' => 'Select a color',
    'multiple'    => 'multiple',
    'style'       => 'width: 150px;'
  ),
),