php如果逻辑计算仅取第一部分值

I have attempted a php if statement which should calculate values basis 2 paramteres:-

Price

Fuel - Petrol or Diesel or LPG or CNG

However - while executing the code - its only calculating the values when fuel type is not diesel

For instance when price is under 600000 and fuel is diesel - it still calculating .04 tax. Can you advise on whats wrong in the code. I have tried reworking - but could not get an answer

Below is Code

   <?php 
   $a = $this->prodDet->v_price;
   $b = $this->prodDet->v_fuel_type;

   if(($a < 600000) && ($b != 'Diesel'))
            {           
                $calculatedtax = (.04*$a);
                echo($calculatedtax);
            }   
   else if(($a < 600000) && ($b == 'Diesel'))
            {           
                $calculatedtax = (.05*$a);
                echo($calculatedtax);
            }

   else if((($a >= 600000) and ($a < 1000000)) and ($b != 'Diesel'))
            {           
                $calculatedtax = (.07*$a);
                echo($calculatedtax);
            }

     else if((($a >= 600000) and ($a < 1000000)) and ($b == 'Diesel'))
            {           
                $calculatedtax = (.0875*$a);
                echo($calculatedtax);
            }               

     else if((($a >= 1000000)) and ($b != 'Diesel'))
            {           
                $calculatedtax = (.10*$a);
                echo($calculatedtax);
            }   
    else if((($a >= 1000000)) and ($b == 'Diesel'))
            {           
                $calculatedtax = (.125*$a);
                echo($calculatedtax);
            }                           
    ?>

Update I checked database value in some fields there's a blank space after Diesel For instance

Fuel Type = Diesel (There's a blank space after diesel word) Fuel Type = Petrol (There's a blank space after diesel word)

when removed this blank space Fuel Type = Diesel(No blank space after diesel word) Fuel Type = Petrol(No blank space after Petrol word)

the calculation happening correctly

Also php logic changed a bit

else if((($a >= 1000000)) and ($b == 'Petrol'))
            {           
                $calculatedtax = (.10*$a);
                echo($calculatedtax);
            }   
else if((($a >= 1000000)) and ($b == 'Diesel'))
            {           
                $calculatedtax = (.125*$a);
                echo($calculatedtax);
             }

Can someone advise how to correct php if statement logic - so that calculation can be performed by ignoring that black space in Fuel type