You can use the active_callback argument to define if you want to hide or display a control under conditions.

The default WordPress Customizer implementation for active_callback allows you to define a callable function or method (see the Customizer API Handbook for details).

Kirki extends the active_callback argument to allow defined field dependencies:

'active_callback' => [
	[
		'setting'  => 'checkbox_demo',
		'operator' => '==',
		'value'    => true,
	]
],

It is formatted as an array of arrays so you can add multiple dependencies.

• setting: you can use the settings argument of the controller-field.
• operator: you can use any of the following:
  • === : uses PHP’s === to evaluate the value
  • ==, =, equal, equals : uses PHP’s == to evaluate the value
  • !== : uses PHP’s !== to evaluate the value
  • !=, not equal : uses PHP’s !== to evaluate the value
  • >=, greater or equal, equal or greater : uses PHP’s >= to evaluate the value
  • <=, smaller or equal, equal or smaller: uses PHP’s <= to evaluate the value
  • >, greater : uses PHP’s > to evaluate the value
  • <, smaller : uses PHP’s < to evaluate the value
  • contains, in : If the context is an array then we’ll check if the value defined exists in the array (using PHP’s in_array() function. If on the other hand the context is a string then we’ll check if the string contains the value defined using PHP’s strpos() and checking not the position of the string but whether the result returns false or not (using === for safety).
• value: the value of the controller-field against which all comparisons and checks will be performed to determin if the field should be visible or not.

In the example below we’re first creating a config, then a section, and finally we add 3 fields to our customizer: a checkbox, a radio and finally a text control.

The text control will only be shown if the value of the checkbox is equal to 1 and the value of the radio control is not equal to option-1.

Kirki::add_config( 'my_config' );

Kirki::add_section( 'my_section', [
	'title'    => esc_html__( 'My Section', 'kirki' ),
    'priority' => 10,
] );

Kirki::add_field( 'my_config', [
	'type'      => 'checkbox',
	'settings'  => 'my_checkbox',
	'label'     => esc_html__( 'My Checkbox', 'kirki' ),
	'section'   => 'my_section',
	'default'   => false,
	'priority'  => 10,
] );

Kirki::add_field( 'my_config', [
	'type'      => 'radio',
	'settings'  => 'my_radio',
	'label'     => esc_html__( 'My Radio', 'kirki' ),
	'section'   => 'my_section',
	'default'   => 'option-1',
	'priority'  => 20,
	'choices'   => [
		'option-1' => esc_html__( 'Option 1', 'kirki' ),
		'option-2' => esc_html__( 'Option 2', 'kirki' ),
		'option-3' => esc_html__( 'Option 3', 'kirki' )
	]
] );

Kirki::add_field( 'my_config', [
	'type'      => 'text',
	'settings'  => 'my_setting',
	'label'     => esc_html__( 'Text Color', 'kirki' ),
	'section'   => 'my_section',
	'default'   => esc_html__( 'my default text here', 'kirki' ),
	'priority'  => 30,
	'active_callback'  => [
		[
			'setting'  => 'my_checkbox',
			'operator' => '===',
			'value'    => true,
		],
		[
			'setting'  => 'my_radio',
			'operator' => '!==',
			'value'    => 'option-1',
		],
	]
] );
?>

The equivalent of the above rule written as a PHP function in the callback would look like this:

'active_callback' => function() {
	$checkbox_value = get_theme_mod( 'my_checkbox', false );
	$radio_value    = get_theme_mod( 'my_radio', 'option-1' );

	if ( true === $checkbox_value && 'option-1' !== $radio_value ) {
		return true;
	}
	return false;
},

or written a lot shorter:

'active_callback' => function() {
	return true === get_theme_mod( 'my_checkbox', false ) && 'option-1' !== get_theme_mod( 'my_radio', 'option-1' );
},

The benefit however of using the field-dependencies using Kirki instead of using a PHP function is that active_callbacks are applied via JavaScript instead of PHP, so changes are instant.