PHP -> SQL Query with Summing

Looking at this, I see that “Paid”, a string, isn’t in quotes. That would cause an error. You can add $wpdb->show_errors() and $wpdb->print_error() methods to reveal that, and any other mysql issues.

Also when querying the database, you should use the $wpdb->prepare() method to escape and prepare your variables for query (yes $user->ID probably can’t be compromised, but it looks like future values in that query might be replaced, or if that value was ever changed in the future to be from $_REQUEST — it’s just always good to escape).

I also used $wpdb->get_var() instead of $wpdb->get_results() as it gives you the single value you’re after which cleans things up a bit. And using $wpdb->prefix instead of wp_ makes the plugin more compatible with other installs should this plugin/theme be released.

add_filter('gform_field_value_user_retainer', 'gform_populate_user_retainer');
function gform_populate_user_retainer($value){
    global $wpdb;
    $user = wp_get_current_user();

    // turn on errors
    $wpdb->show_errors();

    // make the query
    $result = $wpdb->get_var( $wpdb->prepare(
        "
                SELECT SUM(`payment_amount`) as `dviews`
                FROM `{$wpdb->prefix}gf_entry` 
                WHERE `created_by` = %d
                AND `form_id` = 37 
                AND `payment_status` = 'Paid'
        ", 
        $user->ID
    ) );

    // if there was a query error
    if ( $wpdb->last_error !== '' ) {
        return "🔥 Error: " . $wpdb->print_error();
    }

    return $result;
}

If that doesn’t fully solve your issue:

• If you returned "hello world" or 123 in gform_populate_user_retainer(), does the value appear where you expect? If it doesn’t, is gform_field_value_user_retainer the correct hook?

• If you echo "<pre>".$wpdb->prepare("..."); die(); the string query instead of running it, and pasted it into MySQL, does it work? If it doesn’t follow the MySQL error to resolve.

• If you echo "<pre>"; print_r($result);die(); the $result instead of returning it, do you see what you expect to return? If not, revise the query.

• If you echo "<pre>"; print_r($user);die(); do you see what you expect? For yourself and other users? none-users?