CMB2 select field options overridden with a filter and using optgroups

cmb-select-with-optgroups.php

<?php 
function cmb_opt_groups( $args, $defaults, $field_object, $field_types_object ) {
	
	// Only do this for the field we want (vs all select fields)
	if ( '_cmb_option_field' != $field_types_object->_id() ) {
		return $args;
	}

	$option_array = array(
		'Group 1' => array(
			'group1-value1' => 'Value 1',
			'group1-value2' => 'Value 2',
			'group1-value3' => 'Value 3',
		),
		'Group 2' => array(
			'group2-value1' => 'Value 1',
			'group2-value2' => 'Value 2',
			'group2-value3' => 'Value 3',
		),
		'Group 3' => array(
			'group3-value1' => 'Value 1',
			'group3-value2' => 'Value 2',
			'group3-value3' => 'Value 3',
		),
	);

	$saved_value = $field_object->escaped_value();
	$value       = $saved_value ? $saved_value : $field_object->args( 'default' );

	$options_string = '';
	$options_string .= $field_types_object->option( __( 'Select an Option', 'msft-newscenter' ), '', ! $value );

	foreach ( $option_array as $group_label => $group ) {

		$options_string .= '<optgroup label="'. $group_label .'">';

		foreach ( $group as $key => $label ) {
			$options_string .= $field_types_object->option( $label, $key, $value == $key );
		}
		$options_string .= '</optgroup>';
	}

	// Ok, replace the options value
	$defaults['options'] = $options_string;

	return $defaults;
}
add_filter( 'cmb2_select_attributes', 'cmb_opt_groups', 10, 4 );

It looks interesting but I can't really understand how to use that function. Would you please explain how to show such a metabox?

Thank you.

Thanks! Works well, apart from the option method is now select_option, and it takes an array of args. See https://gist.github.com/gyrus/480675f7bbd5d5aec6e0

hi, thanks for the snippet, but i am confused i am trying to use this snippet with in group, how can identify my group id

// Only do this for the field we want (vs all select fields)

if ( '_cmb_option_field' != $field_types_object->_id() ) {
	return $args;
}

thanks