PhP how to calculate moments with variables rows

PHP Snippet 1:

$var1 = 0; $var2 = 0; $count = 0;
foreach($arr as $k=>$v){
    if(is_numeric($v[0]) && is_numeric($v[1])){
        $var2 += $v[0]  * $v[1];
        $var1 += $var2 * ($k + 1);
        $count++;
    }
}
$result = $var1 / $var2;
echo 'Result: ' . $result . '<br /> Count: ' . $count;