无限级分类之查找子孙树和家谱树

子孙树是用递归查找指定栏目的所有子类，以及子类的子类，查找家谱树是查找制定栏目的父类和父类的父类，一致到顶级类

<?php
$area=array(
    array('id'=>'1','name'=>'河南','parent'=>0),
    array('id'=>'2','name'=>'吉林','parent'=>0),
    array('id'=>'3','name'=>'北京','parent'=>0),
    array('id'=>'4','name'=>'信阳','parent'=>1),
    array('id'=>'5','name'=>'郑州','parent'=>1),
    array('id'=>'6','name'=>'长春','parent'=>2),
    array('id'=>'7','name'=>'朝阳','parent'=>3),
    array('id'=>'8','name'=>'海淀','parent'=>3)
    );
//无限级分类之找子孙树
function subtree($arr,$id,$lev=1){
    static $subs=array();//子孙数组

    foreach ($arr as $v) {
        if($v['parent']==$id){
            $v['lev']=$lev;
            $subs[]=$v;
            subtree($arr,$v['id'],$lev+1);
        }
    }
    return $subs;
}
$tree =subtree($area,0,1);
foreach ($tree as $v) {
    echo str_repeat('  ', $v['lev']),$v['name'],'<br/>';
}
// 若不用static，可以用array_merge()将数组连接起来
function subtree2($arr,$id,$lev=1){
    $subs=array();//子孙数组

    foreach ($arr as $v) {
        if($v['parent']==$id){
            $v['lev']=$lev;
            $subs[]=$v;
            $subs=array_merge($subs,subtree2($arr,$v['id'],$lev+1));
        }
    }
    return $subs;
}
$tree2 =subtree2($area,0,1);
foreach ($tree2 as $v) {
    echo str_repeat('  ', $v['lev']),$v['name'],'<br/>';
}

// 无限极分类之查找家谱树
function familytree($arr,$id){
    static $tree=array();

    foreach($arr as $v){
        if($v['id']==$id){
            //判断要不要找父栏目
            if($v['parent']>0){
                familytree($arr,$v['parent']);
            }

            $tree[]=$v;
 
        }
    }
    return $tree;
}
$fam=familytree($area,4);
print_r($fam);

// 迭代找家谱树
function famtree($arr,$id){
    $tree=array();

    while($id!==0){
        foreach($arr as $v){
            if($v['id']==$id){
                $tree[]=$v;
                $id=$v['parent'];
                break;
            }
        }
    }

    return $tree;
}
print_r(famtree($area,4));
?>