Here's a simple program which calculates, to eight decimal places, the value of the Golden Ratio φ implemented in both PHP and Perl, to demonstrate their similarities.

Perl


#!/usr/bin/perl

$a = 1;
$b = 1;
$c = undef;
$psi_old = undef;

print "Approximating psi...\n";
while (1)
{
	$psi = sprintf('%.08f', $b/$a);
	last if ($psi_old eq $psi);
	$psi_old = $psi;
	print "$psi\n";

	$c = $a + $b;
	$a = $b;
	$b = $c;
}

PHP


<?php

$a = 1;
$b = 1;
$c = NULL;
$psi_old = NULL;

print "Approximating psi...\n";
while (1)
{
	$psi = sprintf('%.08f', $b/$a);
	if ($psi_old == $psi) break;
	$psi_old = $psi;
	print "$psi\n";

	$c = $a + $b;
	$a = $b;
	$b = $c;
}

1?>