WordPress at a glance
filter is not described

woocommerce_email_customer_details_fields filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_email_customer_details_fields', 'filter_function_name_778', 10, 3 );
function filter_function_name_778( $array, $sent_to_admin, $order ){
	// filter...

	return $array;
}
$array
-
$sent_to_admin
-
$order
-

Where the hook is called

WC_Emails::customer_details()
woocommerce_email_customer_details_fields
woocommerce/includes/class-wc-emails.php 554
$fields = array_filter( apply_filters( 'woocommerce_email_customer_details_fields', array(), $sent_to_admin, $order ), array( $this, 'customer_detail_field_is_valid' ) );

Where in WP core the hook is used WooCommerce

Usage not found.