<?php
function fibonacci($n)
{
$a = 1;
$b = 1;
for ($i = 0; $i < $n; $i=$i+1)
{
echo "&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;".$a;
$sum = $a+$b;
$a = $b;
$b = $sum;
}
}
echo fibonacci(20);
?>

Output comes like:

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