php 无限分类树形数据格式化

function genTree($items,$id='id',$pid='pid',$son = 'children'){
    $tree = array(); //格式化的树
    $tmpMap = array();  //临时扁平数据
    
    foreach ($items as $item) {
        $tmpMap[$item[$id]] = $item;
    }
    
    foreach ($items as $item) {
        if (isset($tmpMap[$item[$pid]])) {
            $tmpMap[$item[$pid]][$son][] = &$tmpMap[$item[$id]];
        } else {
            $tree[] = &$tmpMap[$item[$id]];
        }
    }
    unset($tmpMap);
    return $tree;
}

$items1 = array(
        array('id' => 1, 'pid' => 0, 'name' => '一级11' ),
        array('id' => 11, 'pid' => 0, 'name' => '一级12' ),
        array('id' => 2, 'pid' => 1, 'name' => '二级21' ),
        array('id' => 10, 'pid' => 11, 'name' => '二级22' ),
        array('id' => 3, 'pid' => 1, 'name' => '二级23' ),
        array('id' => 12, 'pid' => 11, 'name' => '二级24' ),
        array('id' => 9, 'pid' => 1, 'name' => '二级25' ),
        array('id' => 14, 'pid' => 1, 'name' => '二级26' ),
        array('id' => 4, 'pid' => 9, 'name' => '三级31' ),
        array('id' => 6, 'pid' => 9, 'name' => '三级32' ),
        array('id' => 7, 'pid' => 4, 'name' => '四级41' ),
        array('id' => 8, 'pid' => 4, 'name' => '四级42' ),
        array('id' => 5, 'pid' => 4, 'name' => '四级43' ),
        array('id' => 13, 'pid' => 4, 'name' => '四级44' ),
        array('id' => 15, 'pid' => 8, 'name' => '五级51' ),
        array('id' => 16, 'pid' => 8, 'name' => '五级52' ),
        array('id' => 17, 'pid' => 8, 'name' => '五级53' ),
        array('id' => 18, 'pid' => 16, 'name' => '六级64' ),
); 
var_dump(genTree($items1));

function genTree($items,$id='id',$pid='pid',$son = 'children'){
    $tree = array(); //格式化的树
    $tmpMap = array();  //临时扁平数据
    
    foreach ($items as $item) {
        $tmpMap[$item[$id]] = $item;
    }
    
    foreach ($items as $item) {
        if (isset($tmpMap[$item[$pid]])) {
            $tmpMap[$item[$pid]][$son][] = &$tmpMap[$item[$id]];
        } else {
            $tree[] = &$tmpMap[$item[$id]];
        }
    }
    return $tree;
}