Wordpress get post field - php

Question

I am overriding the admin email notification template in WooCommerce and when the order transaction is successful I want to add the transaction id in the email.
I tried $order->get_transaction_id() as explained here in the admin email template, but it returns an empty result.
I then tried this in the admin email template:
do_action('getOrderTransactionID', $order->id);
And in my theme's functions.php I added this but this function doesn't return anything either.
add_action('getOrderTransactionID', 'getOrderTransactionIDForEmail');
function getOrderTransactionIDForEmail($orderId){
echo get_metadata('post', $orderId, '_transaction_id', true);
//get_post_data doesn't return anything either
//get_post_meta( $orderId, '_transaction_id', true);
}
In the wp_postmeta table, the _transaction_id meta key is saved after each successful transaction. Why then am I unable to retrieve the _transaction_id which is already in the database?

Answer 1

What gateway are you using? If you don't see _transaction_id then you need to save the returned transaction_id manually in your gateway plugin. Check out this page
Try saving transaction id in your payment gateway file, then try to see if it displays when you do var_dump(get_post_custom($order->id));
add_post_meta( $order->id, '_transaction_id', YOUR_TRANSACTION_ID, true );

Answer 2

The following is an example of how to add data to email templates using existing hooks.
function kia_display_email_order_meta( $order, $sent_to_admin, $plain_text ) {
$some_field = get_post_meta( $order->id, '_some_field', true ),
$another_field = get_post_meta( $order->id, '_another_field', true ),
if( $plain_text ){
echo 'The value for some field is ' . $some_field . ' while the value of another field is ' . $another_field;
} else {
echo '<p>The value for <strong>some field</strong> is ' . $some_field. ' while the value of <strong>another field</strong> is ' . $another_field;</p>;
}
}
add_action( 'woocommerce_email_order_meta', 'kia_display_email_order_meta', 30, 3 );