Code examples for PHP Infinitus classification (recursive and tree)

function getTree($array, $pid =0, $level = 0){
//声明静态数组,避免递归调用时,多次声明导致数组覆盖 
static $list = []; 
foreach ($array as $key => $value){     
//第一次遍历,找到父节点为根节点的节点 也就是pid=0的节点  
if ($value['pid'] == $pid){
//父节点为根节点的节点,级别为0，也就是第一级
$value['level'] = $level;
//把数组放到list中
$list[] = $value;
//把这个节点从数组中移除,减少后续递归消耗           
unset($array[$key]);           
//开始递归,查找父ID为该节点ID的节点,级别则为原级别+1          
getTree($array, $value['id'], $level+1);
        }
    } 
return $list;
}

function getTree($items,$pid ="pid") {
    $map  = [];
    $tree = []; 
foreach ($items as &$it){ $map[$it['id']] = &$it; }  
//数据的ID名生成新的引用索引树   
foreach ($items as &$at){
        $parent = &$map[$at[$pid]];    
if($parent) {
            $parent['children'][] = &$at;
        }else{
            $tree[] = &$at;
        }
    }
return $tree;
}