无限级分类

$area = array(
array('id'=>1,'name'=>'安徽','parent'=>0),
array('id'=>2,'name'=>'海淀','parent'=>7),
array('id'=>3,'name'=>'濉溪县','parent'=>5),
array('id'=>4,'name'=>'昌平','parent'=>7),
array('id'=>5,'name'=>'淮北','parent'=>1),
array('id'=>6,'name'=>'朝阳','parent'=>7),
array('id'=>7,'name'=>'北京','parent'=>0),
array('id'=>8,'name'=>'上地','parent'=>2)
);

1.递归，查找子孙树

function subtree($arr,$id=0,$lev=1) {$subs = array(); // 子孙数组foreach($arr as $v) {if($v['parent'] == $id) {$v['lev'] = $lev;$subs[] = $v; // 举例说找到array('id'=>1,'name'=>'安徽','parent'=>0),$subs = array_merge($subs,subtree($arr,$v['id'],$lev+1));}}return $subs;
}$tree = subtree($area,0,1);
foreach($tree as $v) {echo str_repeat('  ',$v['lev']),$v['name'],'
';
}

2.递归，求家谱树

家谱树的应用 ,如面包屑导航 首页 > 手机类型 > CDMA手机 > 公益PHP > 递归应用

function familytree($arr,$id) {$tree = array();foreach($arr as $v) {if($v['id'] == $id) { // 判断要不要找父栏目if($v['parent'] > 0) { // parnet>0,说明有父栏目$tree = array_merge($tree,familytree($arr,$v['parent']));}$tree[] = $v; // 以找到上地为例
        }}return $tree;
}print_r(familytree($area,8)); // 北京->海淀->上地

2.迭代，求家谱树

// 迭代,效率比递归高,代码也没多.
// 找家谱树推荐用迭代
function tree($arr,$id) {$tree = array();while($id !== 0) {foreach($arr as $v) {if($v['id'] == $id) {$tree[] = $v;$id = $v['parent'];break;}    }}return $tree;
}print_r(tree($area,8));