Add the product name to the email subject in WooCommerce - php

Question

How can I add the product name in the subject line of this email. is there a list of the available filters for the email subject lines? I'd like to be able to do this without having to write custom php. I'm looking to do something like this:
Completed Order - [{product_name}] ({order_number}) - {order_date}
Below code tried and added in functions.php but subject is not displaying:
add_filter( 'woocommerce_email_subject_customer_completed_order', 'customer_completed_order_subject', 10, 2 );
function customer_completed_order_subject($string,$order){
$fname = $order->billing_first_name;
$lanme = $order->billing_last_name;
$email = $order->billing_email;
$items = $order->get_items();
foreach($items as $meta_key => $items){
$product_name = $items['name'];
$product_id = $items['product_id'];
}
$subject_line = get_field('email_subject',$product_id);
$subject_line = str_replace('{product}',$product_name,$subject_line);
$subject_line = str_replace('{biller_fname}',$fname,$subject_line);
$subject_line = str_replace('{biller_lastname}',$lanme,$subject_line);
$subject_line = str_replace('{biller_email}',$email,$subject_line);
$subject_line = str_replace('{blog_name}',get_bloginfo('name'),$subject_line);
return $subject_line;
}

Answer 1

You are not using the correct hook and there are mistakes… Instead use the following:
add_filter( 'woocommerce_email_format_string' , 'add_custom_email_format_string', 10, 2 );
function add_custom_email_format_string( $string, $email ) {
$order = $email->object; // Get the instance of the WC_Order OBJECT
$order_items = $order->get_items(); // Get Order items
$order_item = reset($order_items); // Get the irst order item
// Replace placeholders with their respective values
$string = str_replace( '{biller_fname}', $order->billing_first_name(), $string );
$string = str_replace( '{biller_lname}', $order->billing_last_name(), $string );
$string = str_replace( '{biller_email}', $order->billing_email(), $string );
$string = str_replace( '{product_name}', $order_item->get_name(), $string );
$string = str_replace( '{blog_name}', get_bloginfo('name'), $string );
return $string;
}
Code goes in function.php file of your active child theme (or active theme). Tested and works.
Note: An order can have many items, so many product names. In the code above, I only keep the first product name…
If you want to handle multiple product names, you will use:
add_filter( 'woocommerce_email_format_string' , 'add_custom_email_format_string', 10, 2 );
function add_custom_email_format_string( $string, $email ) {
$order = $email->object; // Get the instance of the WC_Order OBJECT
$products_names = array();
// Loop through order items
foreach( $order->get_items() as $item ) {
$products_names[] = $item->get_name();
};
// Replace placeholders with their respective values
$string = str_replace( '{biller_fname}', $order->billing_first_name(), $string );
$string = str_replace( '{biller_lname}', $order->billing_last_name(), $string );
$string = str_replace( '{biller_email}', $order->billing_email(), $string );
$string = str_replace( '{product_name}', implode(' ', $products_names), $string );
$string = str_replace( '{blog_name}', get_bloginfo('name'), $string );
return $string;
}
Code goes in function.php file of your active child theme (or active theme). Tested and works.
Related: Add a custom placeholder to email subject in WooCommerce