Ok so I figured this out.

benf — Thu, 25 Feb 2010 12:12:37 +0000

Ok so I figured this out. First I replace all occurances of HTML tags with spaces using this function:

function striptags ($str) {
 return trim(strip_tags(str_replace('<', ' <', $str)));
}

and then use the below while loop and preg_match_all using the given regex (\b either side is the key) to count the amount of times the keyword occurs:

  while($row = mysql_fetch_array($query)){
        if (preg_match("/\b$row[0]\b/i",$url) > 0){
          $count = preg_match_all("/\b$row[0]\b/i",$url,$match);
          $s[$x] = array('word'=>$row[0],'occur'=>$count); 
        }
        $x++;
   }