var maxConsecutiveAnswers = function(answerKey, k) { let [left, right, numOfTrue, numOfFalse, max] = new Array(5).fill(0); const moreChanges = () => numOfTrue > k && numOfFalse > k; while (right < answerKey.length) { if(answerKey[right] === 'T') numOfTrue++; if(answerKey[right] === 'F') numOfFalse++; while(moreChanges()) { if(answerKey[left] === 'T') numOfTrue--; if(answerKey[left] === 'F') numOfFalse--; left++; } max = Math.max(max, right - left + 1); right++; } return max; };

$arr = array(1, 2, 3, 4);
foreach ($arr as &$value) {
    $value = $value * 2;
}
// $arr is now array(2, 4, 6, 8)
unset($value); // break the reference with the last element