system/classes/Collection.php
public function sumByKey($key = false)
    {
        $collection = $this->getIterator();
        $sum = 0;
        foreach ($collection as $result) {
            if ($key && isset($result->$key)) {
                $sum += $result->$key;
            }
            else if ($key && isset($result[$key])) {
                $sum += $result[$key];
            }
            else {
                $sum += $result;
            }
        }
        return $sum;
    }
public function sumByKey($key = false)
    {
        $collection = $this->getIterator();
        $sum = 0;
        foreach ($collection as $result) {
            if ($key && isset($result->$key)) {
                $sum += $result->$key;
            }
            else if ($key && isset($result[$key])) {
                $sum += $result[$key];
            }
            else {
                $sum += $result;
            }
        }
        return $sum;
    }
public function sumByKey ( $ key = false ) { $ collection = $ this -> getIterator ( ) ; $ sum = 0 ; foreach ( $ collection as $ result ) { if ( $ key && isset ( $ result -> $ key ) ) { $ sum += $ result -> $ key ; } else if ( $ key && isset ( $ result [ $ key ] ) ) { $ sum += $ result [ $ key ] ; } else { $ sum += $ result ; } } return $ sum ; }
Returns the sum of the contents of the Container.
If given a key, will sum that $key->value.
Obviously it's important to have some consistency in the types of resources you
are storing or else the results might not make much sense or could crash.

@param key A key on which to sum the when looking at the contents of this Container.
@return A number.
Returns the sum of the contents of the Container . If given a key will sum that $key - > value . Obviously it s important to have some consistency in the types of resources you are storing or else the results might not make much sense or could crash .