Online PHP editor | output for VRUqg

@ 2014-10-09T11:12:39Z

<?php
$links = [
  [ 1,  3],
  [ 3,  5],
  [ 3,  7],
  [ 3,  9],
  [ 1, 10],
  [10, 15],
];

$input = array_map(function ($link) {
  return ['id' => $link[1], 'parent' => $link[0]];
}, $links);

function buildTreeMap($input, $child = 'id', $parent = 'parent') {
  $map = array();

  foreach ($input as $node) {
    // init self
    if (!array_key_exists($node[$child], $map)) {
      $map[$node[$child]] = [];
    }

    // init parent
    if (!array_key_exists($node[$parent], $map)) {
      $map[$node[$parent]] = [];
    }

    // add to parent
    $map[$node[$parent]][$node[$child]] =& $map[$node[$child]];
  }

  return $map;
}

print_r(
  buildTreeMap($input)
);

Output for 5.4.0 - 5.4.45, 5.5.24 - 5.5.35, 5.6.8 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6: Array ( [3] => Array ( [5] => Array ( ) [7] => Array ( ) [9] => Array ( ) ) [1] => Array ( [3] => Array ( [5] => Array ( ) [7] => Array ( ) [9] => Array ( ) ) [10] => Array ( [15] => Array ( ) ) ) [5] => Array ( ) [7] => Array ( ) [9] => Array ( ) [10] => Array ( [15] => Array ( ) ) [15] => Array ( ) )
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29: Parse error: syntax error, unexpected '[' in /in/VRUqg on line 2
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1, 5.0.0 - 5.0.5: Parse error: parse error, unexpected '[' in /in/VRUqg on line 2
Process exited with code 255.
Output for 4.3.2 - 4.3.4: Parse error: parse error in /in/VRUqg on line 2
Process exited with code 255.

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