PHP Threads class supports thread based tasks. The run() method of the Thread will be executed when invoked. Multi-thread sometimes is useful, e.g. when you download a lot of files, and some urls may be slow. The following code can download urls using multi-threads.

<?PHP
error_reporting(E_ALL);
class dn extends Thread
{
    public $res    = '';
    public $name   = '';
    public $runing = false;
	public $wfile;

    public function __construct($name) {
        $this->res    = 'Running Fisrt Time ...\n';
        $this->param    = 0;
        $this->runing = true;
		$this->wfile = "";
    }

    public function run() {
        while ($this->runing) {
            if ($this->param != "")
			{
				downloadurl($this->param,$this->wfile);
                $this->param   = '';
            }
			else {
				sleep(1);
            }
        }
    }
}

function downloadpages()
{
	$webpath="http://www.endmemo.com/program/php/";
	$pages = array("arraydiff","arraykeys","asort","ksort",
	        "array","cookie","arraypush","copy","substr");
	$wdir = "c:/test/";
	$sticks[] = new dn('a');
	$sticks[] = new dn('b');
	$sticks[] = new dn('c');
	$sticks[] = new dn('d');
	$sticks[] = new dn('e');

	foreach ($sticks as $w) {
		$w->start();
		$w->param="w";
	}

	$num = count($pages);
	for ($ii=0; $ii<$num;$ii++)
	{
 		$wfile = $wdir . $pages[$ii] . ".htm";
		$url = webpath . $pages[$ii] . ".php";
		
		while (true)
		{
			foreach ($sticks as $worker)
			{
				if ($worker->param=='')
				{
					$worker->param = $url;
					$worker->wfile = $wfile;
					break 2;
				}
			}
		}
	}
}

function downloadurl($url, $wfile)
{
	$res = file_get_contents($url);
	if (strlen($res)>10)
	{
		$newf = fopen ($wfile, "wb");
		if ($newf) fwrite($newf,$res);
		fclose($newf);
	}	
}

downloadpages();
?>