How to display the sum of the TV variable of child elements in MODx Revo?

Question

MODX

Please help with an article or a link to the plugin - I've looked all over and can't find it.
I have no knowledge in php (only at the level of form handlers). I need to display in MODx the sum of all values ​​of a variable of child elements.
In general, here is the link hm.newway.site/keyjsyi.html
there there are values ​​​​like everything done by projects, for the amount, etc. - I want to make sure that these values ​​are calculated automatically.

Answer 1

Here is a primitive snippet. Call it whatever you want and call it in the right place on the page.
Just replace parent => 10 with the id of the container for which you want to calculate the amount, and num with the name of the TV you want to calculate.

$count = 0;
$pdo = $modx->getService('pdoFetch');
$resources = $pdo->getCollection('modResource', array('parent' => 10), array('includeTVs' => 'num'));
foreach ($resources as $res) {
   $count = $count + $res['num']
}
return $count;