Light Build Sequence

light-bulb-sequence.php

<?php
    $firstSeqArr = [];
    $secondSeqArr = [];
    $operations = 0;
    while($str = fgets(STDIN)){
        $trimmedStr = trim($str);
        $trimmedStrSplit = str_split($trimmedStr);
          if(empty($firstSeqArr)) {
              $firstSeqArr = $trimmedStrSplit;
          } else {
            $trimmedStrSplit = str_split(substr($trimmedStr, 0, count($firstSeqArr) - 1));
            $secondSeqArr = $trimmedStrSplit;
          }
    }
    function isCharArrMatching($matchee, $matcher) {
        return implode("", $matchee) === implode("", $matcher);
    }
    $firstSeqLen = count($firstSeqArr);
    $loopLimit = ceil($firstSeqLen/2);
    for($index = 0; $index < $loopLimit; $index++) {
        $loopLimit = $index - 1;
        if(isCharArrMatching($firstSeqArr, $secondSeqArr)) {
            break;
        }
        $backwardIndex = $firstSeqLen - 1 - $index;
        $startingChar = $firstSeqArr[$index];
        $lastChar = $firstSeqArr[$backwardIndex];
        if($startingChar !== @$secondSeqArr[$index]) {
            $inserted = array($startingChar);
            if(array_key_exists($index, $secondSeqArr) && count($secondSeqArr) === $firstSeqLen) {
                $secondSeqArr[$index] = $startingChar;
            } else {
                array_splice( $secondSeqArr, $index, 0, $inserted );
            }
            
        }
        if($lastChar !== @$secondSeqArr[$backwardIndex]) {
            $inserted = array($lastChar);
            if(array_key_exists($backwardIndex, $secondSeqArr)) {
                $secondSeqArr[$index] = $lastChar;
            } else {
                array_splice( $secondSeqArr, $backwardIndex, 0, $inserted );
            }
        }
        $operations++;
    }
    echo isCharArrMatching($firstSeqArr, $secondSeqArr) ? $operations : NULL;
?>