counting number of rows using a JOIN table and hierarchical data.

Hi there, I am storing hierarchical info about zones and a list of projects in my database. They are being displayed using the first function shown below. This works fine. I am now trying to create another function that will count the number of projects that is listed in the root zone and also all of its child zones. For example say i have the zone structure

>webdesign
>>php
>>asp

and the root zone is webdesign, I would want the function to output a count of all projects in webdesign + php + asp. The aim is that the function can be used to count any given "root" zone. I have made a crude attempt but all it returns is 0. Here it is:

////////////////////////////////////////////////////////////// COUNT THE PROJECTS
function countzone_projects($root, $searchstring) {
   // retrieve the left and right value of the $root node
   $rootzoneprojects = 0;
   $result = mysql_query('SELECT nleft, nright FROM zones '.
                          'WHERE zone_ID="'.$root.'";');
   $row = mysql_fetch_array($result);

   // start with an empty $right stack
   $right = array();
      $zoneinfo = array();
   // now, retrieve all descendants of the $root node
   $result = mysql_query('SELECT zone_ID, zone_Name, nleft, nright FROM zones '.
                          'WHERE nleft BETWEEN '.$row['nleft'].' AND '.
                          $row['nright'].' ORDER BY nleft ASC;');

   // display each row
   while ($row = mysql_fetch_array($result)) {
       // only check stack if there is one
       if (count($right)>0) {
           // check if we should remove a node from the stack
           while ($right[count($right)-1]<$row['nright']) {
               array_pop($right);
           }
       }
        
         $subzoneid = $row['zone_ID'];
                           //for each subzone find out how many projects there are for it including searchstring.
            $subzonesql =  " link_projects_zones.zone_ID   =   {$subzoneid}";
            $subzonesearchstring = $subzonesql . $searchstring;
            $subzonetotalsql = "SELECT COUNT(*) FROM projects JOIN link_projects_zones ON projects.proj_ID = link_projects_zones.proj_ID WHERE" . $subzonesearchstring;
            $result = mysql_query($subzonetotalsql);
            $r = mysql_fetch_row($result);
            $numrows = $r[0];
                        
                        //add that number to the total count for the root zone. ($rootzoneprojects)
                        $rootzoneprojects + $numrows;
                        
                        
       // display indented node title
        //echo str_repeat('>',count($right));


       // add this node to the stack
       $right[] = $row['nright'];
   }
   return $rootzoneprojects;
}
////////////////////////////////////////////////////////////////////////////////

my overall aim is to generate ouput like so
webdesign (300 projects)
>>php(200 projects)
>>asp(100 projects)

I hope I have explained myself clearly enough! Thanks for the help

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/////////////////////////////////////////////////////////////CREATE ARRAY WITH TREE INFO:
 
function display_tree($root) {
   // retrieve the left and right value of the $root node
   $result = mysql_query('SELECT nleft, nright FROM zones '.
                          'WHERE zone_ID="'.$root.'";');
   $row = mysql_fetch_array($result);
 
   // start with an empty $right stack
   $right = array();
	$zoneinfo = array();
   // now, retrieve all descendants of the $root node
   $result = mysql_query('SELECT zone_ID, zone_Name, nleft, nright FROM zones '.
                          'WHERE nleft BETWEEN '.$row['nleft'].' AND '.
                          $row['nright'].' ORDER BY nleft ASC;');
 
   // display each row
   while ($row = mysql_fetch_array($result)) {
       // only check stack if there is one
       if (count($right)>0) {
           // check if we should remove a node from the stack
           while ($right[count($right)-1]<$row['nright']) {
               array_pop($right);
           }
       }
	   
	   			$array_row['zone_ID'] = $row['zone_ID'];
				$array_row['nright'] = $row['nright'];
				$array_row['nleft'] = $row['nleft'];
				$array_row['zone_Name'] = $row['zone_Name'];
				$array_row['zone_Description'] = $row['zone_Description'];
				$array_row['zone_indent'] = count($right);
				$array_row['zone_numberofprojects'] = count($right);
				$zoneinfo[] = $array_row;
				
       // display indented node title
        //echo str_repeat('>',count($right)); 
 
 
       // add this node to the stack
       $right[] = $row['nright'];
   }
   return $zoneinfo;
   //print_r($zoneinfo);
}