php - Modifications to nested array elements do not stick -

i either working through fatigue barrier or else have serious gap in understanding of php. here need do

• i have array (a) of arrays (a)
• i need iterate through outer array and
• for each of inner arrays need add new element, in turn array
• this sort of code churn out many times day , had expected little trouble it. however, surprise whilst can modify a cannot make modifications stick , appear in a

here code

function fillroutenames($routes,$export) {  for($i=0;$i < count($routes);$i++)   {   $route = $routes[$i];   trigger_error(gettype($route));//shows array, expected   $disps = $route['d'];   $nd = array();   foreach($disps $disp) $nd[] = fxnname($disp,$export);   //now have new element want add  $route['nd'] = $nd;  trigger_error(json_encode($route));  /as expected output shows new element, nd }    trigger_error(json_encode($routes)); //but gone - never did $oute['nd'] = $nd 

}

there must blindingly obvious here wrong have been unable figure out. hope here spot issue.

thats because $route copy of inner array. need add reference or use direct index $routes[$i]. this:

function fillroutenames($routes,$export) {     for($i=0;$i < count($routes);$i++)      {         $route = &$routes[$i];// add reference          trigger_error(gettype($route));          $disps = $route['d'];         $nd = array();         foreach($disps $disp) $nd[] = fxnname($disp,$export);          $routes[$i]['nd'] = $nd;// or use index          trigger_error(json_encode($route));     }        trigger_error(json_encode($routes)); }