How do you find a sum of a specific range in a PHP array?

[SubhanUllah]

$array = [1, 2, 3, 4, 6, 7, 8]; 
 
$from = 2;  // array offset 1 
$to = 4;  // array offset 4 
$sum = 0; 
 
for($i = $from; $i <= $to; $i++ ){ 
  $sum = $sum + $array[$i]; 
} 
 
echo $sum; // 15