Show specific database value in notification email

Hi
what i want to do is to show a specific value from the database in the booking notification e-mail. As i am missing good php knowledge, this is all but trivial to me. I tried for many hours to find a solution, but couldn’t get it and think i have to give it up, if noone can help me with this.

I think, the way it should work is like this: As i can use PLACEHOLDERS in the E-Mail options it should be the best way to make a custom placeholder for that database-field.

I found the following code, what seemed to me is close to that what i want to do, but to tell the true is that i have nearly no clue what the line with $replace should look. All the tutorials on the official page are way to complicated.

This is my code for functions.php so far:

/* Adding Bookinginfo Placeholder */

function placeholder_bookinginfo($replace, $EM_Bookings_Table, $result){
global $wp_query, $wp_rewrite;
switch( $result ){
case ‘#_BOOKINGADRESS’:
$replace = get_??( ‘booking_info’, $EM_Booking_Table->??? );
}
return $replace;
}

add_filter(’em_event_output_placeholder’,’placeholder_bookinginfo’,1,3);

Maybe there are still chances for small wonders 🙂
We will see

https://wordpress.org/plugins/events-manager/