PHP - Sitemap Crawler and Generator

<?
/*************************************************************

Sitemap Crawler and Generator

*************************************************************/

    $file = "google.xml";       // output file
    $url = "http://www.plop.at";    // url to scan

    // ignore urls starting with
    $skip[0] = "http://www.plop.at/print"; 
    $skip[1] = "http://www.plop.at/slide";
    
    $extension = ".html";       // scan files with extension

    $freq = "daily";            // google scan frequency
    $priority = "0.5";          // site priority
    

function Path ($p)
{
    $a = explode ("/", $p);
    $len = strlen ($a[count ($a) - 1]);
    return (substr ($p, 0, strlen ($p) - $len));
}

function GetUrl($url)
{
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $data = curl_exec($ch);
    curl_close($ch);
    return $data;
}

function Scan($url)
{
    global $scanned, $pf, $extension, $skip, $freq, $priority;
    
    echo "scan url $url\n";

    array_push ($scanned, $url);
    $html = GetUrl ($url);
    $a1 = explode ("<a", $html);

    foreach ($a1 as $key => $val)
    {
    $parts = explode (">", $val);
    $a = $parts[0];
    
    $aparts = explode ("href=", $a);

    $hrefparts = explode (" ", $aparts[1]);
    $hrefparts2 = explode ("#", $hrefparts[0]);

    $href = str_replace ("\"", "", $hrefparts2[0]);
    
    if ((substr ($href, 0, 7) != "http://") && 
       (substr ($href, 0, 8) != "https://") &&
       (substr ($href, 0, 6) != "ftp://"))
    {
        if ($href[0] == '/')
        $href = "$scanned[0]$href";
        else
        $href = Path ($url) . $href;
    }
    
    if (substr ($href, 0, strlen ($scanned[0])) == $scanned[0])
    {
        $ignore = false;
        if (isset ($skip))
        foreach ($skip as $k => $v)
            if (substr ($href, 0, strlen ($v)) == $v)
            $ignore = true;
        
        if ((!$ignore) &&
        (!in_array ($href, $scanned)) && 
        (strpos ($href, $extension) > 0)        
        )
        {
        fwrite ($pf, "<url>\n  <loc>$href</loc>\n" .
                 "  <changefreq>$freq</changefreq>\n" .
                 "  <priority>$priority</priority>\n</url>\n");
        echo $href. "\n";
        Scan ($href);
        }
    }
    }
}

                        


    $pf = fopen ($file, "w");
    if (!$pf)
    {
    echo "cannot create $file\n";
    return;
    }

    fwrite ($pf,"<?xml version=\"1.0\" encoding=\"UTF-8\"?>
<urlset
      xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\"
      xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"
      xsi:schemaLocation=\"http://www.sitemaps.org/schemas/sitemap/0.9
            http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd\">
<!-- created with Plop PHP Google Sitemap Generator 0.2 www.plop.at -->

<url>
  <loc>$url/</loc>
  <changefreq>daily</changefreq>
</url>
");

    $scanned = array();
    Scan ($url);
    
    fwrite ($pf, "</urlset>\n");
    fclose ($pf);
?>