[     {"id":1,"name":"人事","pid":0,"level":0,"son":[{"id":3,"name":"招聘部","pid":1,"level":1,"son":[{"id":7,"name":"研发部","pid":3,"level":2,"son":[]},{"id":8,"name":"行政部","pid":3,"level":2,"son":[]}]},{"id":4,"name":"人事部","pid":1,"level":1,"son":[]}]},     {"id":2,"name":"技术部","pid":0,"level":0,"son":[{"id":5,"name":"研发部","pid":2,"level":1,"son":[]},{"id":6,"name":"运维部","pid":2,"level":1,"son":[]}]} ]

function groupbylevel($tree) {     $result = [];     foreach ($tree as $node) {         $result[$node['level']][] = $node;         if (!empty($node['son'])) {             $result = array_merge($result, groupbylevel($node['son']));         }     }     return $result; }

$result = groupbylevel($tree);

[     0 => [         {"id":1,"name":"人事","pid":0,"level":0,"son":[...]},         {"id":2,"name":"技术部","pid":0,"level":0,"son":[...]},     ],     1 => [         {"id":3,"name":"招聘部","pid":1,"level":1,"son":[...]},         {"id":4,"name":"人事部","pid":1,"level":1,"son":[...]},         {"id":5,"name":"研发部","pid":2,"level":1,"son":[...]},         {"id":6,"name":"运维部","pid":2,"level":1,"son":[...]},     ],     2 => [         {"id":7,"name":"研发部","pid":3,"level":2,"son":[]},         {"id":8,"name":"行政部","pid":3,"level":2,"son":[]},     ], ]