查询无限极分类

/**
 * User: finn.lee
 * Date: 2016/3/5 14:25
 */
$rows = array(
    0=>array(
        'cat_id' => 1,
        'name' => 'dev',
        'pid' => 0
    ),
    1=>array(
        'cat_id' => 2,
        'name' => 'php',
        'pid' => 1
    ),
    2=>array(
        'cat_id' => 3,
        'name' => 'smarty',
        'pid' => 2
    ),
    3=>array(
        'cat_id' => 4,
        'name' => 'life',
        'pid' => 0
    ),
    4=>array(
        'cat_id' => 5,
        'name' => 'pdo',
        'pid' => 2
    ),
    5=>array(
        'cat_id' => 6,
        'name' => 'pdo-mysql',
        'pid' => 5
    ),
    6=>array(
        'cat_id' => 7,
        'name' => 'java',
        'pid' => 1
    )
);

// 72648
// 84072

function findChild(&$arr,$id){

    $childs=array();
    foreach ($arr as $k => $v){
        if($v['pid']== $id){
            $childs[]=$v;
        }
    }
    return $childs;
}
function build_tree($root_id){
    global $rows;
    $childs=findChild($rows,$root_id);
    if(empty($childs)){
        return null;
    }
    foreach ($childs as $k => $v){
        $rescurTree=build_tree($v['cat_id']);
        if( null !=   $rescurTree){
            $childs[$k]['childs']=$rescurTree;
        }
    }
    return $childs;
}


$tree=build_tree(0);

echo memory_get_usage();

print_r($tree);

注: $rows是活的 ， $root_id是活的