php problem

I'm learning php and Mysql , i'm copy script for teaching from project professional book whatever when running this script :

<?php
$host="localhost";
$dbusername="root";
$dbpassword="root";
$database="books";
$x=mysql_connect("localhost","root","root") or die(mysql_error());


$x2=mysql_select_db($books);

if (empty ($category))
{
$category=1;
}
$childval=$category;
$query = "Select categoryid,name from categroy where categoryid=\"".$childval."\"";
$result=mysql_query($query);
if ($row=@mysql_fetch_array($result))
{
 $catid[1]=$row["categoryid"];
 $catname[1]=$row["name"];
}
while (!($childval==0))
{
 $query="select parentcategoryid from category where categoryid=\"".$childval."\"";
$result=mysql_query($query);
if ($row=@mysql_fetch_array($result))
{
    $childval=$row["parentcategoryid"];
    $query="select categoryid,name from category where categoryid=\"".$childval."\"";
    $result=mysql_query($query);
    if($row=mysql_fetch_array($result))
    {
        $catid[]=$row["categoryid"];
        $catname[]=$row["name"];
 }
}
}

for ($i=count($catname);$i>0;$i)
{
    echo "<A href=visitor.php?category=".$catid[$i].">".$catname[$i]."</a>>";
}
?>

The problem appears :Fatal error: Maximum execution time of 180 seconds exceeded in C:\AppServ\www\project.php on line 32