PHP script for printing first 20 Fibonacci numbers

<?php
$count = 0 ;
$f1 = 0;
$f2 = 1;
echo $f1." , ";
echo $f2." , ";
while ($count < 20 )
{
$f3 = $f2 + $f1 ;
echo $f3." , ";
$f1 = $f2 ;
$f2 = $f3 ;
$count = $count + 1;
}
?>

Its output will be 

0 , 1 , 1 , 2 , 3 , 5 , 8 , 13 , 21 , 34 , 55 , 89 , 144 , 233 , 377 , 610 , 987 , 1597 , 2584 , 4181 , 6765 , 10946