Bitmap Holes

BitmapHoles.php

<?php
/**
 * Bitmap Holes
 * Have the function BitmapHoles(strArr) take the array of strings stored in strArr, 
 * which will be a 2D matrix of 0 and 1's, and determine how many holes, or contiguous regions of 0's,
 * exist in the matrix. A contiguous region is one where there is a connected group of 0's going
 * in one or more of four directions: up, down, left, or right. 
 * 
 * For example: if strArr is ["10111", "10101", "11101", "11111"], then this looks like the following matrix:
 * 
 * 1 0 1 1 1
 * 1 0 1 0 1
 * 1 1 1 0 1
 * 1 1 1 1 1
 * 
 * For the input above, your program should return 2 because there are two separate contiguous regions of 0's, which create "holes" in the matrix. You can assume the input will not be empty.
 */


function checkHole($row, $column, $array)
{
    // previous
    if ($column >= 1 && $array[$row][$column - 1] == '0') {
        $array[$row][$column - 1] = 'H';
        $array = checkHole($row, $column - 1, $array);
    }

    // next
    if (isset($array[$row][$column + 1]) && $array[$row][$column + 1] == '0') {
        $array[$row][$column + 1] = 'H';
        $array = checkHole($row, $column + 1, $array);
    }

    // up
    if ($row - 1 >= 0 && $array[$row - 1][$column] == '0') {
        $array[$row - 1][$column] = 'H';
        $array = checkHole($row - 1, $column, $array);
    }

    // down
    if ($row + 1 <= (count($array) - 1) && $array[$row + 1][$column] == '0') {
        $array[$row + 1][$column] = 'H';
        $array = checkHole($row + 1, $column, $array);
    }

    return $array;
}

function SearchingChallenge($strArr)
{

    $holeCount = 0;
    $zerosRemain = true;

    while ($zerosRemain) {
        // we need to traverse
        foreach ($strArr as $key => $val) {
            // flag to indentify if a zero was found
            $foundZero = false;

            // now we need to walk each digit
            foreach (str_split($val) as $stringKey => $stringVal) {

                // check for 0 and mark it!
                if ($strArr[$key][$stringKey] == '0') {
                    // mark it as (H)ole!
                    $strArr[$key][$stringKey] = 'H';
                    // now we need to check other sides: up, down, left, right!!!
                    $strArr = checkHole($key, $stringKey, $strArr);
                    $foundZero = true;
                    $holeCount++;
                }

                if ($stringVal == '1' && $foundZero) {
                    break;
                }
            }

            $zerosRemain = false;
            foreach ($strArr as $key => $val) {
                if (str_contains($val, '0')) {
                    $zerosRemain = true;
                    break;
                }
            }
        }
    }
    // code goes here
    return $holeCount;
}

// keep this function call here
echo SearchingChallenge(fgets(fopen('php://stdin', 'r')));