Php if statement logic with multiple else if. How to make it easy

I am fumbled in between if and else if statement in calculation

Have multiple variable - prime been

Fuel type = (Petrol, Diesel, CNG)

Price = (<600, 600 - 999, > 1000)

Using Php

   <?php  
    $a = $this->prodDet->v_price;
    $h = $this->prodDet->v_fuel_type;
    $x=.02166;
    $y=.02143;
    $z=.02143;

i intend to calculate multiple values subject to combination of price and fuel type

My Question is How to create if statement for doing calculation

    if ($h = Petrol and $a < 600) 
      {
     $c=$a*$z*.85;
   else
      {
    if ($h = Diesel and $a < 600)
     {
     $c=$a*$y*.85;
   else
      {
    if ($h = CNG and $a < 600)
   {
     $c=$a*$x*.85;
   else
      {
     $c=$a*$x*$y*.85;
    if ($h = Petrol and 600 > $a < 1000)
   {
     $c=$a*$y*$z*.85;
   {
   else
      }
    if ($h = Diesel and 600 > $a < 1000)
   {
   else
      }
    if ($h = CNG and 600 > $a < 1000)
    {
   else
      }
    if ($h = Petrol and $a > 1000)
    {
   else
      }
    if ($h = Diesel and $a > 1000)
    {
   else
      }
    if ($h = Diesel and $a > 1000)
    {
   else
      }

Can someone guide to make it easy