Automate sum in array

Question

I will try to explain the problem that I have with this code.

This script works well to up to three persons ($numRows = 3).

$z=0;
$i=0;
$x=0;

do {
    $total[] = (
        ${'contaH'.$z}[$i+0]*$final[$x+0]+
        ${'contaH'.$z}[$i+1]*$final[$x+1]+
        ${'contaH'.$z}[$i+2]*$final[$x+2]
    );
    $z++;
} while ($z<$numRows); //3

But if I have only four persons ($numRows = 4), I need something like this:

$z=0;
$i=0;
$x=0;

do {
    $total[] = (
        ${'contaH'.$z}[$i+0]*$final[$x+0]+
        ${'contaH'.$z}[$i+1]*$final[$x+1]+
        ${'contaH'.$z}[$i+2]*$final[$x+2]+
        ${'contaH'.$z}[$i+3]*$final[$x+3]
        // if they are 5 persons ($numRows=5), here, should exists another row
    );
    $z++;
} while ($z<$numRows); //4

So the problem is to automate these changes in relation of $numRows.

Here is a demo of matrix algebra:

The only thing that I want is put my code dynamically in a function of number of persons.

A   |  B |  C |  D
Person1
Person2
Person3
Person4
...

What can be different in my case is just the number of persons.

More information here.

Answer 1

$z=0;
$i=0;
$x=0;
$numRows = 5;

do{
    $currentSum = 0;
    for($c = 0; $c < $numRows; $c++){
        $currentSum += (${'contaH'.$z}[$i+$c] * $final[$x+$c]);
    }
    $total[] = $currentSum;
    $z++;
}while($z < $numRows);