php - Change Variable Value in While Looping -

i want know how modify variable value each time while looping.

please guide me doing wrong in below coding.

$amount = 500;  while ($amount > 0) { $a = $amount - 50; echo $a . "<br>"; }

i receiving this:

450 450 450 450 450 450 450 450 450

but want that:

450 400 350 300 250 200 150 100 50

you not changing the amount in loop, hence getting result 450 form statement:

$a = $amount - 50;

which evaluates time $a = 500 - 50 = 450

change code this:

$amount = 500;  while ($amount > 0) { $a = $amount - 50; echo $a . "<br>"; $amount  = $amount - 50;  }

Sher