PHP Program for Find the number of islands | Set 1 (Using DFS)

<?php 
// Program to count islands 
// in boolean 2D matrix

$ROW = 5;
$COL = 5;

// A function to check if a 
// given cell (row, col) can 
// be included in DFS
function isSafe(&$M, $row, $col,
                &$visited)
{
    global $ROW, $COL;
    
    // row number is in range,
    // column number is in 
    // range and value is 1 
    // and not yet visited
    return ($row >= 0) && ($row < $ROW) &&     
           ($col >= 0) && ($col < $COL) &&     
           ($M[$row][$col] && 
             !isset($visited[$row][$col])); 
}

// A utility function to do DFS
// for a 2D boolean matrix. It 
// only considers the 8 neighbours
// as adjacent vertices
function DFS(&$M, $row, $col,
            &$visited)
{
    // These arrays are used to
    // get row and column numbers 
    // of 8 neighbours of a given cell
    $rowNbr = array(-1, -1, -1, 0, 
                    0, 1, 1, 1);
    $colNbr = array(-1, 0, 1, -1, 
                    1, -1, 0, 1);

    // Mark this cell as visited
    $visited[$row][$col] = true;

    // Recur for all 
    // connected neighbours
    for ($k = 0; $k < 8; ++$k)
        if (isSafe($M, $row + $rowNbr[$k], 
                $col + $colNbr[$k], $visited))
            DFS($M, $row + $rowNbr[$k], 
                $col + $colNbr[$k], $visited);
}

// The main function that returns
// count of islands in a given 
// boolean 2D matrix
function countIslands(&$M)
{
    global $ROW, $COL;
    
    // Make a bool array to 
    // mark visited cells. 
    // Initially all cells 
    // are unvisited
    $visited = array(array());

    // Initialize count as 0 and
    // traverse through the all 
    // cells of given matrix
    $count = 0;
    for ($i = 0; $i < $ROW; ++$i)
        for ($j = 0; $j < $COL; ++$j)
            if ($M[$i][$j] && 
                 !isset($visited[$i][$j])) // If a cell with value 1
            {                               // is not visited yet, 
                DFS($M, $i, $j, $visited); // then new island found 
                ++$count;                   // Visit all cells in this 
            }                               // island and increment 
                                           // island count.

    return $count;
}

// Driver Code
$M = array(array(1, 1, 0, 0, 0),
           array(0, 1, 0, 0, 1),
           array(1, 0, 0, 1, 1),
            array(0, 0, 0, 0, 0),
           array(1, 0, 1, 0, 1));

echo "Number of islands is: ",
            countIslands($M);

// This code is contributed 
// by ChitraNayal 
?>