<?php

/**
 * Binding references from variables to deep array and object structures.
 * 
 * joon park - joon@dvessel.com
 */


function &_select_reference(&$elements, $selection) {

  // Clean and convert selection strings into a flat array.
  // Uses ">" to delimit each value.
  if (!empty($selection) && is_string($selection)) {
    $selection = explode('>', str_replace(array(' '), '', $selection));
  }

  return _sub_select($elements, $selection);
}


function &_sub_select(&$elements, &$selection) {

  // Keep traversing in recursive calls. Always maintain reference.
  foreach ($selection as $i => $select) {
    // Treat arrays and objects the same for consistency.
    if (is_array($elements) && isset($elements[$select])) {
      $element_child = &$elements[$select];
    }
    elseif (is_object($elements) && isset($elements->$select)) {
      $element_child = &$elements->$select;
    }
    else {
      // A miss. Break out and do nothing.
      $return_element = FALSE;
      break;
    }

    // Recurse.
    unset($selection[$i]);
    $return_element = &_sub_select($element_child, $selection);
  }

  // If $return_element is not set, then the target was found.
  if (!isset($return_element)) {
    $return_element = &$elements;
  }

  return $return_element;
}



// Example: ==================================================================

$var['member_a']['sub_member_a']['sub_sub_member_a'] = 'AAA';
$var['member_a']['sub_member_b']['sub_sub_member_c'] = 'ABC';
$var['object']->member['a']['b']['c'] = 'Object:ABC';


// Traverse through array keys to bind reference.
$sub_element = &_select_reference($var, 'member_a > sub_member_a > sub_sub_member_a');

$sub_element = 'AAX';

print var_dump($var);
// Outputs:
// array(2) {
//   ["member_a"]=>
//   array(2) {
//     ["sub_member_a"]=>
//     array(1) {
//       ["sub_sub_member_a"]=>
//       &string(3) "AAX"                   << referenced through $sub_element
//     }
//     ["sub_member_b"]=>
//     array(1) {
//       ["sub_sub_member_c"]=>
//       string(3) "ABC"
//     }
//   }
//   …


$object_deep_c = &_select_reference($var, 'object > member > a > b > c');

$object_deep_c = 'Object:ABX';

print var_dump($var);
// Outputs:
// array(2) {
//   …
//   ["object"]=>
//   object(stdClass)#1 (1) {
//     ["member"]=>
//     array(1) {
//       ["a"]=>
//       array(1) {
//         ["b"]=>
//         array(1) {
//           ["c"]=>
//           &string(10) "Object:ABX"     << referenced through $object_deep_c
//         }
//       }
//     }
//   }
// }