Alternative validation

gistfile1.php

    function validation($data, $files) {
        $errors = parent::validation($data, $files);

        // Check if any item quantities were selected.
        // Retrieve order items and amounts.

        // First assume the user has not selected anything.
        $allempty = true;
        // Loop through all of the form fields.
        foreach ($data as $field => $value) {
            // filter the select boxes
            if ($strpos($field, '_type')) {
                if ($value != 0) {
                    // At least one checkbox was selected.
                    $allempty = false;
                }
                // Add an error to each field.
                $allerrors[$field] = get_string('zeroamount', 'block_realexpayments');
            }
        }
        // Turns out we all is really empty, return the errors
        if ($allempty) {
            return $allerrors;
        }
    }