Add Your Own Custom Checkout Fields

<?php

// add fields
add_action( 'woocommerce_after_checkout_billing_form', 'misha_select_field' );
add_action( 'woocommerce_after_order_notes', 'misha_subscribe_checkbox' );
 
// save fields to order meta
add_action( 'woocommerce_checkout_update_order_meta', 'misha_save_what_we_added' );
 
// select
function misha_select_field( $checkout ){
 
	// you can also add some custom HTML here
 
	woocommerce_form_field( 'contactmethod', array(
		'type'          => 'select', // text, textarea, select, radio, checkbox, password, about custom validation a little later
		'required'	=> true, // actually this parameter just adds "*" to the field
		'class'         => array('misha-field', 'form-row-wide'), // array only, read more about classes and styling in the previous step
		'label'         => 'Preferred contact method',
		'label_class'   => 'misha-label', // sometimes you need to customize labels, both string and arrays are supported
		'options'	=> array( // options for <select> or <input type="radio" />
			''		=> 'Please select', // empty values means that field is not selected
			'By phone'	=> 'By phone', // 'value'=>'Name'
			'By email'	=> 'By email'
			)
		), $checkout->get_value( 'contactmethod' ) );
 
	// you can also add some custom HTML here
 
}
 
// checkbox
function misha_subscribe_checkbox( $checkout ) {
 
	woocommerce_form_field( 'subscribed', array(
		'type'	=> 'checkbox',
		'class'	=> array('misha-field form-row-wide'),
		'label'	=> ' Subscribe to our newsletter.',
		), $checkout->get_value( 'subscribed' ) );
 
}
 
// save field values
function misha_save_what_we_added( $order_id ){
 
	if( !empty( $_POST['contactmethod'] ) )
		update_post_meta( $order_id, 'contactmethod', sanitize_text_field( $_POST['contactmethod'] ) );
 
 
	if( !empty( $_POST['subscribed'] ) && $_POST['subscribed'] == 1 )
		update_post_meta( $order_id, 'subscribed', 1 );
 
}