Codeigniter：向数组添加新项

I'm creating a large array of info ready to be exported as a csv.

I'm having trouble adding additional items to the array.

I've looked at the php manual and loads of other resources, but I'm unable to get it to work?

All the work is done in my controller

public function payments_export()
    {
        $parents = $this->Swim_model->CRUD_read_parents();
        foreach ($parents->result() as $parentsrow)
        {
            if($parentsrow->AdultID > 1000010)
            {
            $data[] = array(
                'First Name' => $parentsrow->AdultFirstName,
                'Surname' => $parentsrow->AdultLastName,
                'Email' => $parentsrow->EmailName,
            );

Lots more processing to produce $owes

                $owes = number_format(array_sum($children) - $autodiscount, 2);
                if($owes != 0)
                {
                $data['Fees'] = $owes;
                }
            }
        }

So I create the array $data and store three bits of info in it - lots of processing later produces $owes (which is correct), but when I try to add it to the same row in the array, it doesn't?

The foreach loop should then go through each parent and add another row to the array containing the four items on each row.