Type: mixed
Possible values: Either a string or an array containing the desired class name(s). If using a string, class names should be separated by spaces.

Allows the addition of custom CSS classes to a form field. Any field may use this parameter.

Example: Adding a single class

'class' => 'my-class'

Example: Adding a multiple classes using a string

'class' => 'my-class anotherclass'

Example: Adding multiple classes using an array

'class' => array('my-class', 'anotherclass')