3v4l.org

run code in 150+ php & hhvm versions
Bugs & Features
<?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 - 7.1.0
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 - 5.3.29
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 - 4.4.1, 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.