3v4l.org

run code in 150+ php & hhvm versions
Bugs & Features
<?php $array = array( 55 => array( 'ident' => 'test 1', 'depth' => 1, ), 77 => array( 'parent_id' => 55, 'ident' => 'test 2', 'depth' => 2, ), 109 => array( 'parent_id' => 77, 'ident' => 'test 3', 'depth' => 3, ), 78 => array( 'parent_id' => 55, 'ident' => 'test 4', 'depth' => 2, ), 25 => array( 'ident' => 'test 5', 'depth' => 1, ) ); foreach ($array as $key => &$sub) { if (isset($sub['parent_id'])) { $array[$sub['parent_id']]['children'][$key] = &$sub; } } unset($sub); // unset the reference to make sure to not overwrite it later... // now remove the entries with parents foreach ($array as $key => $sub) { if (isset($sub['parent_id'])) unset($array[$key]); } var_dump($array); print_r($array);
Output for 5.0.0 - 5.6.21, hhvm-3.12.0, 7.0.0 - 7.1.0
array(2) { [55]=> array(3) { ["ident"]=> string(6) "test 1" ["depth"]=> int(1) ["children"]=> array(2) { [77]=> array(4) { ["parent_id"]=> int(55) ["ident"]=> string(6) "test 2" ["depth"]=> int(2) ["children"]=> array(1) { [109]=> array(3) { ["parent_id"]=> int(77) ["ident"]=> string(6) "test 3" ["depth"]=> int(3) } } } [78]=> array(3) { ["parent_id"]=> int(55) ["ident"]=> string(6) "test 4" ["depth"]=> int(2) } } } [25]=> array(2) { ["ident"]=> string(6) "test 5" ["depth"]=> int(1) } } Array ( [55] => Array ( [ident] => test 1 [depth] => 1 [children] => Array ( [77] => Array ( [parent_id] => 55 [ident] => test 2 [depth] => 2 [children] => Array ( [109] => Array ( [parent_id] => 77 [ident] => test 3 [depth] => 3 ) ) ) [78] => Array ( [parent_id] => 55 [ident] => test 4 [depth] => 2 ) ) ) [25] => Array ( [ident] => test 5 [depth] => 1 ) )
Output for hhvm-3.10.0

Process exited with code 153.
Output for 4.4.2 - 4.4.9
Parse error: syntax error, unexpected '&', expecting T_VARIABLE or '$' in /in/hKYve on line 28
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.4.1
Parse error: parse error, unexpected '&', expecting T_VARIABLE or '$' in /in/hKYve on line 28
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error, expecting `T_VARIABLE' or `'$'' in /in/hKYve on line 28
Process exited with code 255.