usort(): The argument should be an array

[Remember14a@xxxxxxx]

No this doesnt solve error.
let me give you more details to understand problem with the said code.

go to this link, please.

http://www.abcdefg.us/search/search.php

in search enter, 
Justice, you get response without an error.

Now enter law,

you get error, pasted below,

Warning: usort(): The argument should be an array in 
/home2/wwwabcde/public_html/search/searchfuncs.php on line 300
------------------------------------------------------------------
below is part of the code and few lines of code above and below the error 
point, as the code is more tha 300 lies I had to paste tail  end of code at the 
point of error.
  ----------------------------------------------------------------------

$row[4];

   $res[$i]['size'] = $row[5];

   $res[$i]['weight'] = $result_array[$row[0]];

   $i++;

  }
  usort($res, "cmp"); 

  echo mysql_error();

  $res['maxweight'] = $maxweight;

  $res['results'] = $results;

  return $res;

 /**/

 }

?>