php syntax error on line 9

I have been staring at this for an hour now. It says I have an
Parse error: syntax error, unexpected '{' in line 9.

Could someone please look at this for me. Thanks in advance.

if(isset($_POST['submit']))

{
 function foo($a, $b)
{
   foreach(array_keys($a) as $i)
   {
      if(array_key_exists($i, $b){
          $result[$i] = $a[$i]*$b[$i];
      }else{
          $result[$i] = 0;
      }

   }
   foreach(array_keys($b) as $i)
   {
      if(not array_key_exists($i, $a){ //exists in b but not i a
          $result[$i] = 0;
      }
   }
   return $result
}
}


?>