Hi Alayna,
Welcome to BuddyDev.

The code snippet is old and from the time when bp_activity_add_meta was not part of BuddyPress. You most probably put that code in bp-custom.php and that’s why you are getting the error. if it was put in functions.php, It would not have generated the error.

Please remove the cold code and use the following code in your bp-custom.php

function bpdev_track_user_favorite( $activity_id, $user_id ) {

    bp_activity_add_meta( $activity_id, 'favorited_by_user', $user_id );
}
add_action( 'bp_activity_add_user_favorite', 'bpdev_track_user_favorite', 10, 2 );

function bpdev_track_user_unfavorite( $activity_id, $user_id ){

    bp_activity_delete_meta( $activity_id, 'favorited_by_user', $user_id );
}
add_action( 'bp_activity_remove_user_favorite', 'bpdev_track_user_unfavorite', 10, 2 );
//show faces, yay!

function bpdev_show_who_favorited_activities() {
    $output = '';
    $favorited_users = bp_activity_get_meta( bp_get_activity_id(), 'favorited_by_user' );
    //print_r($favorited_users);
    if ( ! empty( $favorited_users ) ) {

        foreach ( (array) $favorited_users as $user_id ) {
            $output .= "<a href='" . bp_core_get_user_domain ( $user_id ) . "'>". bp_core_fetch_avatar ( array( 'type'=> 'thumb', 'height'=> 25, 'width'=>25, 'item_id'=> $user_id ) ) . "</a>";
        }
            

    }
    if ( $output ) {
        echo "<div class='clearfix activity-favorited-by'>{$output}</div>";
    }
        
}
add_action( 'bp_activity_entry_content', 'bpdev_show_who_favorited_activities' );

After putting this code try favoriting an activity and reloading the page to see it works or not. It should work.

Please do let me know if it is working for you or not?

Thank you
Ravi

Hi Alayna

Thank You for confirming. I am glad that i could help.

Thank You
Ravi

Hello Stefan,

With BuddyBoss you do not need this as recently introduced reactions features. Please take a look at that.

Regards
Ravi