Refactoring array index magic number with class constant.

During a code review my peer Michal Mazur turned me onto the follow example; I have to say I am really digging it: Array Index as constant .

In my specific case here is the usage:

if (!empty($paramData[19]) && is_string($paramData[19])) {
    $paramData = $paramData[19];
} elseif (empty($paramData[19]) && !empty(isset($paramData[17])) && isset($paramData[17])) {
    $paramData = $paramData[17];
}

…and the refactored logic:

if (!empty($rowData[$this::FULL_SOURCE]) && is_string($rowData[$this::FULL_SOURCE])) {
    $imageSource = $rowData[$this::FULL_SOURCE];
} elseif (empty($rowData[$this::FULL_SOURCE]) && !empty(isset($rowData[$this::SQUARE_SOURCE])) &&
    isset($rowData[$this::SQUARE_SOURCE])
) {
    $imageSource = $rowData[$this::SQUARE_SOURCE];
}

While a bit more verbose the logic is much easier to read using the contextually named constants.