why is this loop so slow?

babygodzilla

is there a reason why the following loop runs rather slow? it takes about 20 seconds to process the whole thing. i tried both foreach and for loops and the results are the same

$servers = array("mars","venus","mercury");
$courses = array("AB1","AB2","AB3");
$quarters = array("Fall","Winter","Spring","SSI","SSII");
$years = array("2004","2005");


foreach($servers as $server) {
	echo "<td>\n<table width='100%' border='0'>\n<tr>\n<th align='left'>$server</th>\n</tr>\n<tr><td>\n";
	foreach($courses as $course) {
		foreach($quarters as $quarter) {
			foreach($years as $year) {
				$url = "http://".$server.".ucdavis.edu/".$course."/".$quarter.$year."/Login/Login.cfm";
				if($fp=@fopen($url,"r")) {
					echo "<a href='$url'>$course $quarter $year</a><br/>\n";
				}
			}
		}
	}
	echo "</td></tr>\n</table>\n</td>\n";
}

any way to speed it up?

THANKS!!

colinhorne

Yes:

You are opening a pointer to a remote file all the time, which is going to take forever.

What's more, you're not even using the $fp.

Solution (asuming you are going to use $fp):

Open $fp before you go into the loop

Otherwise:

Remove all the $fp stuff

Note: On my PC, it fails to connect to the server, which adds to the script exe. time

Cheers

babygodzilla

thanks for replying !

failed to connect to server? im not sure i noe what u mean. this script is supposed to check if that URL is valid and if so, makes a link. but im sure u already knew that :p

i removed the $fp stuff, but didnt help much...

colinhorne

Yep, just realised that now...

If you run this script:

<?php
$servers = array("mars","venus","mercury");
$courses = array("AB1","AB2","AB3");
$quarters = array("Fall","Winter","Spring","SSI","SSII");
$years = array("2004","2005");


foreach($servers as $server) {
    echo "<td>\n<table width='100%' border='0'>\n<tr>\n<th align='left'>$server</th>\n</tr>\n<tr><td>\n";
    foreach($courses as $course) {
        foreach($quarters as $quarter) {
            foreach($years as $year) {
                $url = "http://".$server.".ucdavis.edu/".$course."/".$quarter.$year."/Login/Login.cfm";
                echo "<a href='$url'>$course $quarter $year</a><br/>\n";
            }
        }
    }
    echo "</td></tr>\n</table>\n</td>\n";
}
?>

It runs almost instantly.

Try running this script (php5):

<?php

  $start = microtime(true);

  @fopen("http://www.google.com", "r");

  $end = microtime(true);

  echo $end-$start;

?>

Now run this one:

<?php

  $start = microtime(true);

  @fopen("http://www.gdoogle.com", "r");

  $end = microtime(true);

  echo $end-$start;

?>

The script for google.com takes 0.15 on my pc. The script for an invalid url takes 11 seconds...

That's where the problem lies :-)

There are over ways to check URLs though, but all will take a while to validate any significant number of urls.

Cheers

babygodzilla

oh thats very interesting to know! thanks!

colinhorne

BTW: A quick way to validate a host (not full url) is:

gethostbyname() - http://uk2.php.net/manual/en/function.gethostbyname.php

That would check that a domain name resolves to an IP address

Cheers