Web Crawler in MySql

I recently built a search engine and would like a step by step procedure on how to install and run a web crawler.

mysql_connect("localhost", "root", "") or die(mysql_error());
mysql_select_db("searchengine")or die(mysql_error());



$clean = mysql_real_escape_string($_GET['search']);
$hello = mysql_query("SELECT * FROM search WHERE Site_title = '$clean'") or die(mysql_error());
if(mysql_num_rows($hello) >= 1) {
    while($i = mysql_fetch_array($hello)) {
        echo '<a href="'.$i['site_link'].'">'.$i['Site_title'].'</a><p>'.$i['site_description']. '</P>';
    }
}
 else{
     echo "No Results Found For :(";
 }

?> Thanks