Det(A)

<?php
$A[0][0] = 1;
$A[0][1] = 2;
$A[0][2] = 4;
$A[0][3] = 6;
$A[1][0] = 3;
$A[1][1] = 2;
$A[1][2] = 1;
$A[1][3] = 4;
$A[2][0] = -1;
$A[2][1] = 4;
$A[2][2] = 3;
$A[2][3] = -5;
$A[3][0] = -2;
$A[3][1] = -4;
$A[3][2] = -3;
$A[3][3] = 5;



echo "|A|=" .  det($A);
function det($A){
    //echo "|A|" . count($A);
    //if $A is a 1x1 matrix return the number formatted as a number
    if(count($A)==1){
        return $A[0][0];
    }else{
        //value will hold the adding up of each crossing out thing
        $value = 0;
        //polarity will be switched to follow...
/*
+-+
-+-
+-+
*/
        $polarity = 1;
        for($i=0;$i<count($A);$i++){
            //echo "i:" . $i . "<br />";
            //create the sub matrix
            $y=0;
            for($n=0;$n<count($A);$n++){
            //not the current column (its been crossed out)
            if($n!=$i){
                //start at 1 because row 0 has been crossed out
                for($m=1;$m<count($A[$n]);$m++){
                    //if the array B is defined write to it otherwise create it and write to it
                    $B[$y][$m-1] = $A[$n][$m];
                }
                //echo "y:" . $y . "<br />";
                $y++;
            }
            }
            $value = $value + $polarity * $A[$i][0] * det($B);
            $polarity = $polarity * -1;
        }
        return $value;
    }
}
?>