Add custom field to the check-out booking form

add_filter('sln.checkout.additional_fields',function(){
return array(
'custom_field_a'=> array(
"label" => 'Custom field A',
"type" => 'text',
"width" => 'full',
"default" => 'Your default value',
"customer_profile" => true
),
'custom_field_b'=> array(
"label" => 'Custom field B',
"type" => 'textarea',
"width" => 'half',
"default" => 'Your default value'
),
'custom_field_c'=> array(
"label" => 'Custom field C',
"type" => 'select',
"options" => array('option_a','option_b', 'option_c'),
"width" => 'half',
"default" => 'option_a'

),
'custom_field_d'=> array(
"label" => 'Custom field D',
"type" => 'checkbox'
),

);
});

To add custom fields to the front-end check-out booking form copy and paste this code inside your theme functions.php file and change the fields according to your needs.

Fields types

These are the fields type available:

• Text
• Textarea
• checkbox
• select

Fields parameters

For each field you can specify these parameters:

• label
• type
• options ( if is a "select" type )
• width ( half, full, quarter )
• default value ( a text string for the text fields or 'true/false' for the checkbox )
• customer_profile ( 'true/false' ) for those fields that belong to the customer personal details 
• customer_profile ( 'booking_hidden' ) if you don't want to show this fields inside the  check-out booking form but only on the "Booking My Account" page inside the "Personal data" tab.

Fields management

The custom fields can be managed from "Settings > Check-out" section of Salon Booking settings