Question

I’m trying to assemble this JSON object of Baobab data (tree structure). I have the following recursive function:

/* Takes the Tree (in this case, always '1') and the Parent ID where we want to start, this case, I would also start with '1' */
function walkTree($tree, $id)
{
     /* Gets the children of that of that ID */
     $children = $tree->getChildren($id);

     $data = "";

     /* Loop through the Children */
     foreach($children as $index => $value) 
     {
          /* A function to get the 'Name' associated with that ID */
          $name = getNodeName($tree, $value);

          /* Call the walkTree() function again, this time based on that Child ID */
          $ret = walkTree($tree, $value);

          /* Append the string to $data */
          $data .= '{"data":"'.$name.'","attr": {"id" : "'.$value.'"}
                   ,"state":"closed","children": ['.$ret.']}';
     }

     /* Return the final result */
     return $data;
}

This is very close to working but as you see, there are no commas between each nested object and array, so the JSON is improperly formatted. Lots of the following:

… {"data":"Personal","attr": {"id" : "4"},"state":"closed","children": []}{"data":"News-editorial","attr": {"id" : "5"},"state":"closed","children": []…

I believe the best way would be to create a Php array and json_encode() it, but I can’t find a way to make the nested Objects work.

Answer 1

Well if you wanted to build this out through concatenation then just keep track of the first and subsequent elements. This modified code should work:

/* Takes the Tree (in this case, always '1') and the Parent ID where we want to start, this case, I would also start with '1' */
function walkTree($tree, $id)
{
  /* Gets the children of that of that ID */
  $children = $tree->getChildren($id);
  $first = true;

  $data = "";

  /* Loop through the Children */
  foreach($children as $index => $value) 
  {
    /* A function to get the 'Name' associated with that ID */
    $name = getNodeName($tree, $value);

    /* Call the walkTree() function again, this time based on that Child ID */
    $ret = walkTree($tree, $value);

    /* Append the string to $data */
    if($first) {
       $first = false;
    } else {
      /*add comma for each element after the first*/
      $data .= ',';
    }
    $data .= '{"data":"'.$name.'","attr": {"id" : "'.$value.'"},"state":"closed","children": ['.$ret.']}';
  }

  /* Return the final result */
  return $data;
}