无限级分类查找--子孙树，家谱树

$area=array(
array(‘id‘=>1,‘name‘=>‘北京‘,‘parent‘=>0),
array(‘id‘=>2,‘name‘=>‘昌平‘,‘parent‘=>1),
array(‘id‘=>3,‘name‘=>‘海淀‘,‘parent‘=>2),
array(‘id‘=>4,‘name‘=>‘天津市‘,‘parent‘=>0),
array(‘id‘=>5,‘name‘=>‘市辖区‘,‘parent‘=>4),
array(‘id‘=>6,‘name‘=>‘和平区‘,‘parent‘=>5),
array(‘id‘=>7,‘name‘=>‘河北省‘,‘parent‘=>0),
array(‘id‘=>8,‘name‘=>‘石家庄市‘,‘parent‘=>7),
array(‘id‘=>9,‘name‘=>‘长安区‘,‘parent‘=>8)
);

/**
 * 找子树，子节点
 */
function findson($arr,$id=0)
{
    $sons=array();
    foreach ($arr as $value) {
        if ($value[‘parent‘]==$id) {
            $sons=$value;
        }
    }
    return $sons;
}

print_r(findson($area,0));

/**
 * 找子孙树
 */
function subtree($arr,$id,$lev=1)
{
     $subs=array();
    foreach ($arr as $value) {
        if ($value[‘parent‘]==$id) {
            $value[‘lev‘]=$lev;
            $subs[]=$value;
            $subs=array_merge($subs,subtree($arr,$value[id],$lev+1));
        }
    }

    return $subs;

}

/**
 * 家谱树
 */
function familytree($arr,$id)
{static $tree=array();
    foreach ($arr as $value) {
        if ($value[‘id‘]==$id) {
            $tree[]=$value;
            if ($value[‘parent‘]>0) {
                familytree($arr,$value[‘parent‘]);
            }   
        }
    }
    return $tree;

}