Creating a Sitemap Generator, Getting Error

I have been creating a sitemap generator with a friend of mine, and it has been going great until now. I had just uploaded the script to my site, and was going to release it, but I found a huge problem. No matter what URL I input, it didn't want to read it. I have attached the code, and you can find a semi-working version at http://programmingseo.com/site.php

<?php


# The site url to crawl.
if(IsSet($_REQUEST['starturl'])){
    $siteurl = ($_REQUEST['starturl']);
}

# The frequency of updating.
if(IsSet($_REQUEST['freq'])){
    $frequency = ($_REQUEST['freq']);
}

# Priority of page in relation to other parts of site.
if(IsSet($_REQUEST['start_priority'])){
    $priority = ($_REQUEST['start_priority']);
}

# Include last modification date.
if(IsSet($_REQUEST['mod_date'])){
    $lastmodification = ($_REQUEST['mod_date']);   //working on this
}

# File extensions to include.
$extensions = array("htm", "html", "php", "asp", "pdf");

# Try to index dynamic web pages that have a parameter in there url (?). Valid options
# are true or false. Use this at your own risk, could capture session info
# which possibly could cause problems during the Google index process.

if(IsSet($_REQUEST['index_dynpages'])){
    $index_dynamic_pages_params = ($_REQUEST['index_dynpages']);
}


# Gets a URLs path minus the actual filename + query.
function getPath($url) {
    if($GLOBALS['index_dynamic_pages_params'] == true){
        $url = explode("?", $url);
        $url = $url[0];
    }

    $temp = explode("/", $url);
    $fnsize=strlen($temp[(count($temp) - 1)]);
    return substr($url, 0, strlen($url) - $fnsize);
}

# Cleans up a path so that extra / slashes are gone, translated, etc
function cleanPath($url) {
	$new = array();
	$url = explode("/", trim($url));
	foreach($url as $p){
            $p = trim($p);
            if($p != "" && $p != "."){
                if($p == ".."){
                    if(is_array($new))$new = array_pop($new);
                }else{
                    $new = array_merge((array) $new, array($p));
                }
            }
	}

	$url = $new[0]."/";
	for($i=1; $i < count($new); $i++){
            $url .= "/".$new[$i];
        }

	return $url;
}

# Checks if URL has specified extension, if so returns true
function checkExt($url, $ext){
    # Strip out parameter info from a script (?)
    if($GLOBALS['index_dynamic_pages_params'] == true){
        $url = explode("?", $url);
        $url = $url[0];
    }

    $text=substr($url, strlen($url) - (strlen($ext) + 1), strlen($url));
    if($text == ".".$ext){
        return true;
    }else{
        return false;
    }
}

# Retrieve Site URLs
function getUrls($url, $string) {
    $type = "href";
    # Regex to chop out urls
    preg_match_all("|$type\=\"?'?`?([[:alnum:]:?=&@/._-]+)\"?'?`?|i", $string, $matches);
    $ret[$type] = $matches[1];

    # Make all URLS literal (full path)
    for($i=0; $i<count($ret['href']); $i++){
        if(!preg_match( '/^(http|https):\/\//i' , $ret['href'][$i])){
            $ret['href'][$i] = getPath($url)."/".$ret['href'][$i];
        }
        $ret['href'][$i] = cleanPath($ret['href'][$i]);
    }

    return $ret;
}

function addUrls($urls) {
    if(is_array($urls)){
        for($i=0; $i < count($urls['href']); $i++){
            $skip = 0;

            # Cycle through to make sure url is unique
            for($x=0; $x < count($GLOBALS['urls']); $x++){
                if($GLOBALS['urls'][$x] == $urls['href'][$i]){
                    $skip = 1;
                    break;
                }

                # Check extension
                $extgood = 0;
                foreach($GLOBALS['extensions'] as $ext){
                    if(checkExt($urls['href'][$i], $ext))$extgood = 1;
                }

                # Make sure its in the current website
                if(!stristr($urls['href'][$i], $siteurl))$skip = 1;
                if($skip == 0 && $extgood == 1)$GLOBALS['urls'][] = $urls['href'][$i];
            }
        }
    }
}

function getNextUrl($oldurl) {
    if($oldurl == "")return $GLOBALS['urls'][0];

    for($i=0; $i < count($GLOBALS['urls']); $i++){
        if($GLOBALS['urls'][$i] == $oldurl){
            if(isset($GLOBALS['urls'][($i+1)])){
                return $GLOBALS['urls'][($i+1)];
            }else{
                return false;
            }
        }
    }
    return false;
}

$urls = array($siteurl);

$turl = "";
# Cycle through tree and build a url list
while($turl = getNextUrl($turl)){
    # Extend script time limit
    set_time_limit(120);
    $html='';

    # Read html file into memory
    if($html == file($turl)){ // You're setting $html = $turl, use double equal signs
        $html = stripslashes(implode($html));
        print($turl."\n");

        # Get site urls from html and add new unique url to list if needed
        addUrls(getUrls($turl, $html));
    }else{
        print("Failed reading URL: $turl\n");  
    }
}


function generateSitemap(){
    $xml_string = '<?xml version="1.0" encoding="UTF-8"?><urlset xmlns="http://www.google.com/schemas/sitemap/0.84" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.google.com/schemas/sitemap/0.84 http://www.google.com/schemas/sitemap/0.84/sitemap.xsd">';

    foreach($urls as $url){ 
        $xml_string .= "<url><loc>$urls</loc><changefreq>$frequency.</changefreq><priority>$priority.</priority></url>\n";
    }

    $xml_string .= "</urlset>";
    print("\nDumping result to screen...\n<br /><br /><br />\n\n\n");
    print('<textarea rows="25" cols="70" style="width:100%">'.$xml_string.'</textarea>');
}
?>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.1 Transitional//EN">
<html>
    <head>
        <title>Sitemap Generator - ProgrammingSEO.com</title>
        <style type="text/css">
            a {color:blue;text-decoration:none;}
            a:hover {color:red;}
        </style>
    </head>
    <body>
        <h1>Google Sitemap Generator</h1>

        <?php
            if(IsSet($_POST['action'])){
              if($_POST['action'] == 'Create Sitemap')generateSitemap();
            }
        ?>

        <h2>Settings</h2>

        <form action="site.php" method="post">
            Site URL: <input type="text" name="starturl" size="30" value ="http://yoursite.com/"/><br/>
            <br/>Priority : <input type="text" name="start_priority" size="3" value="1.0" /> Priority of page in relation to other parts of your site. A number from 0.1 to 1.0 is acceptable. <br/>
            <br/>Change Frequency <br/>
            <input type="radio" name="" value="always" /> Always<br/>
            <input type="radio" name="" value="hourly" /> Hourly<br/>
            <input type="radio" name="" value="daily" /> Daily<br/>
            <input type="radio" name="" value="weekly" /> Weekly<br/>
            <input type="radio" name="" value="monthly" /> Monthly<br/>
            <input type="radio" name="" value="yearly" /> Yearly<br/>
            <input type="radio" name="" value="never" /> Never<br/><br/>
            <br/>Post the Last Modification Date?<br/> <input type="radio" checked="checked" name="mod_date" value ="true" /> Yes<br/>
            <input type="radio" name="mod_date" value ="false" /> No <br/> <br/>
            <br/>Index Dynamic Pages?<small> (May index sessions!)</small><br/> <input type="radio" checked="checked" name="index_dynpages" value ="true" /> Yes<br/>
            <input type="radio" name="index_dynpages" value ="false" /> No <br/> <br/>
            <input type="submit" name="action" value="Go!" />
        </form>
    </body>
</html>

PHP:

I greatly appreciate any help, I've spent a few days trying to debug this. I know it's probably something obvious, but I'm pretty new. Thanks again.