PHP Program to Efficiently compute sums of diagonals of a matrix

<?php
// A simple PHP program to
// find sum of diagonals
$MAX = 100;

function printDiagonalSums($mat, $n)
{
    global $MAX;
    $principal = 0;
    $secondary = 0;
    for ($i = 0; $i < $n; $i++) 
    {
        for ($j = 0; $j < $n; $j++) 
        {

            // Condition for 
            // principal diagonal
            if ($i == $j)
                $principal += $mat[$i][$j];

            // Condition for
            // secondary diagonal
            if (($i + $j) == ($n - 1))
                $secondary += $mat[$i][$j];
        }
    }

    echo "Principal Diagonal:" , 
               $principal ,"
";
    echo "Secondary Diagonal:", 
              $secondary ,"
";
}

// Driver code
$a = array (array ( 1, 2, 3, 4 ), 
            array ( 5, 6, 7, 8 ), 
            array ( 1, 2, 3, 4 ), 
            array ( 5, 6, 7, 8 ));
printDiagonalSums($a, 4);

// This code is contributed by ajit
?>

<?php
// An efficient PHP program 
// to find sum of diagonals
$MAX = 100;

function printDiagonalSums($mat, $n)
{
    global $MAX;
    $principal = 0; $secondary = 0; 
    for ($i = 0; $i < $n; $i++) 
    {
        $principal += $mat[$i][$i];
        $secondary += $mat[$i][$n - $i - 1];     
    }

    echo "Principal Diagonal:" ,
               $principal ,"
";
    echo "Secondary Diagonal:" , 
               $secondary ,"
";
}

// Driver Code
$a = array(array(1, 2, 3, 4),
           array(5, 6, 7, 8), 
           array(1, 2, 3, 4),
           array(5, 6, 7, 8));
printDiagonalSums($a, 4);

// This code is contributed by aj_36 
?>