Example form is linked to a database table, but won't be saved in this example.
When you submit the form, the value is presented with debug_dump(), so strings are quoted and array values listed.
<?php $field = new form_field_fields($form, 'Estimate'); $field->input_add('V', ['size' => 3]); $field->input_add('U', array('options' => ['hours' => 'Hours', 'days' => 'Days'])); $field->required_error_set('The estimate is required.'); $field->invalid_error_set('An invalid estimate value has been set.'); ?>