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run code in 150+ php & hhvm versions
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<?php $array = array( 55 => array( 'ident' => 'test 1', 'depth' => 1, ), 77 => array( 'parent_id' => 55, 'ident' => 'test 2', 'depth' => 2, ), 109 => array( 'parent_id' => 77, 'ident' => 'test 3', 'depth' => 3, ), 78 => array( 'parent_id' => 55, 'ident' => 'test 4', 'depth' => 2, ), 25 => array( 'ident' => 'test 5', 'depth' => 1, ) ); function v1($array) { 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]); } return $array; } function push_at_key($what, $what_key, $key, $array) { foreach($array as $k => $v) { if($key == $k) { $array[$k]['children'][$what_key] = $what; return $array; } } foreach($array as $k => $v) { $array[$k] = push_at_key($what, $what_key, $key, $v['children']); } return $array; } function v2($array) { $out = array(); foreach ($array as $key => $sub) { if(!isset($sub['parent_id'])) { $out[$key] = $sub; } else { $out = push_at_key($sub, $key, $sub['parent_id'], $out); } } return $out; } //var_dump(v1($array)); var_dump(v2($array));
Output for 5.0.0 - 5.6.28, hhvm-3.10.0 - 3.12.0, 7.0.0 - 7.1.0
array(2) { [55]=> array(2) { [77]=> array(4) { ["parent_id"]=> int(55) ["ident"]=> string(6) "test 2" ["depth"]=> int(2) ["children"]=> array(1) { [109]=> array(3) { ["parent_id"]=> int(77) ["ident"]=> string(6) "test 3" ["depth"]=> int(3) } } } ["children"]=> array(1) { [78]=> array(3) { ["parent_id"]=> int(55) ["ident"]=> string(6) "test 4" ["depth"]=> int(2) } } } [25]=> array(2) { ["ident"]=> string(6) "test 5" ["depth"]=> int(1) } }
Output for 4.4.2 - 4.4.9
Parse error: syntax error, unexpected '&', expecting T_VARIABLE or '$' in /in/pR20F on line 30
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 '$' in /in/pR20F on line 30
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error, expecting `T_VARIABLE' or `'$'' in /in/pR20F on line 30
Process exited with code 255.