Fibonacci Sequence in PHP

<?php

$num =20;

$a = 0;

$b = 1;

echo $a."</br>";

echo $b."</br>";

for($i = 1; $i <= $num; $i++)

{

    $c = $a+$b;

    echo $c."</br>";

    $a = $b;

    $b = $c;

}

?>