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/*

# SUBJECT FILTERS

woocommerce_email_subject_new_order
woocommerce_email_subject_customer_processing_order
woocommerce_email_subject_customer_completed_order
woocommerce_email_subject_customer_invoice
woocommerce_email_subject_customer_note
woocommerce_email_subject_low_stock
woocommerce_email_subject_no_stock
woocommerce_email_subject_backorder
woocommerce_email_subject_customer_new_account
woocommerce_email_subject_customer_invoice_paid
 
*/

add_filter( 'woocommerce_email_subject_customer_processing_order', 'change_processing_email_subject', 10, 2 );
 
function change_processing_email_subject( $subject, $order ) {
	
  global $woocommerce;
  $subject = $order->billing_first_name . ', gracias por tu compra en ' . get_bloginfo( 'name', 'display' ) . ' 🦄';
  return $subject;
	
}