WordPress at a glance
filter is not described

woocommerce_email_headers filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_email_headers', 'filter_function_name_7182', 10, 4 );
function filter_function_name_7182( $header, $id, $object, $that ){
	// filter...

	return $header;
}
$header
-
$id
-
$object
-
$that
-

Where the hook is called

WC_Email::get_headers()
woocommerce_email_headers
WC_Emails::low_stock()
woocommerce_email_headers
WC_Emails::no_stock()
woocommerce_email_headers
WC_Emails::backorder()
woocommerce_email_headers
woocommerce/includes/emails/class-wc-email.php 421
return apply_filters( 'woocommerce_email_headers', $header, $this->id, $this->object, $this );
woocommerce/includes/class-wc-emails.php 637
apply_filters( 'woocommerce_email_headers', '', 'low_stock', $product, null ),
woocommerce/includes/class-wc-emails.php 671
apply_filters( 'woocommerce_email_headers', '', 'no_stock', $product, null ),
woocommerce/includes/class-wc-emails.php 709
apply_filters( 'woocommerce_email_headers', '', 'backorder', $args, null ),

Where in WP core the hook is used WooCommerce

Usage not found.