[Don L]

keep in mind this is completely untested, and may not have the intended result at all:

   #
   # Generate additional fields string
   #
   $add_fields_string = '';
     $scorestr="";
     // Add score to fields - LNJ
     if (!empty($data["by_title"]) && count($search_words)>0) {
          $scorestr.="if($sql_tbl[products].product like '%". $data["substring"] ."%',5,0) + ";  //Add high score for exact match - LNJ
          $topscore=4; // Yeah I know HARDCODED - LNJ
          $scoredesc=$topscore/count($search_words); //Get decrementing number for scores - LNJ
          foreach($search_words as $search_word){
               $scorestr.="if($sql_tbl[products].product like '%". $search_word ."%',$topscore,0) + "; //add individual word score - LNJ
          //     $topscore=$topscore-$scoredesc; //Descrement individual score for word - LNJ
          }
     }
     if (!empty($data["by_shortdescr"]) && count($search_words)>0) {
          $scorestr.="if($sql_tbl[products].descr like '%". $data["substring"] ."%',3,0) + ";   //Add high score for exact match - LNJ
          $topscore=2;
          $scoredesc=$topscore/count($search_words);  //Get decrementing number for scores - LNJ
          foreach($search_words as $search_word){
               $scorestr.="if($sql_tbl[products].descr like '%". $search_word ."%',$topscore,0) + "; //add individual word score - LNJ
           //    $topscore=$topscore-$scoredesc;//Descrement individual score for word - LNJ
          }
     }
     if (!empty($data["by_longdescr"]) && count($search_words)>0) {
          $scorestr.="if($sql_tbl[products].fulldescr like '%". $data["substring"] ."%',3,0) + ";    //Add high score for exact match - LNJ
          $topscore=2;
          $scoredesc=$topscore/count($search_words);   //Get decrementing number for scores - LNJ
          foreach($search_words as $search_word){
               $scorestr.="if($sql_tbl[products].fulldescr like '%". $search_word ."%',$topscore,0) + "; //add individual word score - LNJ
            //   $topscore=$topscore-$scoredesc;//Descrement individual score for word - LNJ
          }

     }

     $add_fields[]=$scorestr . " 0 as searchscore";  // Add this field to the list - LNJ
   if(!empty($add_fields) && @is_array($add_fields)) {
      $add_fields_string = ", ".implode(", ", $add_fields);
   }