bill.php

<?php

if(isset($_GET['unit'])) {
  $userunit = $_GET['unit'];
  $bills = array (
       array (
       'min' => 1,
       'max' => 75,
       'price' => 3.8
       ),
       array (
       'min' => 76,
       'max' => 200,
       'price' => 5.14
       ),
       array (
       'min' => 201,
       'max' => 300,
       'price' => 5.36
       ),
       array (
       'min' => 301,
       'max' => 400,
       'price' => 5.63
       ),
       array (
       'min' => 401,
       'max' => 600,
       'price' => 8.7
       ),
       array (
       'min' => 601,
       'max' => 1000000,
       'price' => 9.98
       )
  );

  $billedUnit = $userunit;

  $processed = $billedUnit;
  $totalCost = 0;

  foreach ($bills as &$bill) {
      $amount = NULL;
      if ($processed == 0) {
          break;
      }
      $maxAmount = $bill['max'] - $bill['min'] + 1;
  	if ($maxAmount <= $processed) {
          $amount = $maxAmount;
  	} else {
  	    $amount = $processed;
  	}
    
      $bill['amount'] = $amount;
      $bill['cost'] = $amount * $bill['price'];
      $totalCost += $bill['cost'];
    
      $processed -= $amount;
  }
  
  $totalCost = $totalCost + 55;
  
  $totalCost = ((5 / 100) * $totalCost) + $totalCost;
  
  if(isset($_GET['type'])){
    
    if($_GET['type']=='json'){
      
      header('Content-Type: application/json');
      
      echo json_encode($totalCost);
      
    } 
    
  } else {
    
    echo "Total + Vat: \t $totalCost BDT";
    
  }
  
  

}