Bizarre Results from Calc Element

[nclaypool]

I have a form with a calc element that takes the extended price of a repeating group, adds it up, tacks on the additional fees element then saves that as the grand total.

I've been fiddling with this element for a few days now as it caused all sorts of problems syntax wise when I moved up our PHP version, I've straightened out all the syntax errors but now the calculations are coming back with some unusual results.

$po_id = '{purchase_orders___id}';

$mydb = JFactory::getDbo();

$myquery = $mydb->getQuery(true);

$myquery
  ->select('ext_price')
  ->from('purchase_orders_30_repeat')
  ->where('parent_id = ' . $po_id);
$all_ext_price = $mydb->loadColumn();

$subtotal = array_sum($all_ext_price);
$grand_total = $subtotal + '{purchase_orders___additional_fees}';

return $grand_total;

This is the code as it exists today. As an example I created a test record where the grand total should have come back as $1 but instead came back as $74. I have no idea where its getting the values from that allows it to calculate up to an amount that high.

Any guidance would be greatly appreciated.

 

[nclaypool]

I think I might have figured out where I went wrong here...I was missing the "$mydb->setQuery($myquery);" line.
However, with that line added back in I now get a SQL syntax error: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 3

$po_id = '{purchase_orders___id}';

$mydb = JFactory::getDbo();

$myquery = $mydb->getQuery(true);

$myquery
  ->select('ext_price')
  ->from('purchase_orders_30_repeat')
  ->where('parent_id = ' . $po_id);
 
 
$mydb->setQuery($myquery);
$all_ext_price = $mydb->loadColumn();

$subtotal = array_sum($all_ext_price);
$grand_total = $subtotal + '{purchase_orders___additional_fees}';

return $grand_total;

 

[troester]

In new records '{purchase_orders___id}' will be empty.
Also you won't have the repeat group values in the DB before the record is saved. What should the calc element display in the form?