Question

Given this example, how would I return the result of the equation rather than the equation itself as a string?

$operator = '+';
foreach($resultSet as $item){
    $result = $item[$this->orderField] . $operator . 1;
    echo $result;
}

Answer 1

You could make functions that wrap the operators, or for simplicity just use the bc extension:

$operator = '+';
$operators = array(
  '+' => 'bcadd',
  '-' => 'bcsub',
  '*' => 'bcmul',
  '/' => 'bcdiv'
);

foreach($resultSet as $item){
    $result = call_user_func($operators[$operator], $item[$this->orderField], 1);
    echo $result;
}