Chain of Responsibility

chain.php

<?php

class Handler
{
    protected $next;
    protected $id;
    protected $limit;

    public function getLimit()
    {
        return $this->limit;
    }

    public function handler($id, Handler $handler = null)
    {
        $this->id = $id;
        $this->limit = $id * 1000;
        $this->next = $handler;
    }

    public function handleRequest($data)
    {
        if ($this->getLimit() > $data) {
            return "Request for " . $data . " handled at level " . $this->id;
        } elseif (null !== $this->next) {
            return $this->next->HandleRequest($data);
        } else return ("Request for " . $data . " handled BY DEFAULT at level " . $this->id);
    }
}

function echoLn($var)
{
    echo "{$var}<br />\n";
}

$start = null;

for ($i = 5; $i > 0; $i--)
{
    echoLn("Handler " . $i . " deals up to a limit of " . ($i * 1000));
    $start = new Handler($i, $start);
}

foreach (array(50, 2000, 1500, 10000, 175, 4500) as $i)
{
    echoLn($start->handleRequest($i));
}