2种分类数组的群组（转自网络）

<?php
  //数组
  //parentid是父类的id
  $rows = array( 
    array( 
        ‘id‘ => 1, 
        ‘name‘ => ‘dev‘, 
        ‘parentid‘ => 0 
    ), 
    array( 
        ‘id‘ => 2, 
        ‘name‘ => ‘php‘, 
        ‘parentid‘ => 1 
    ), 
    array( 
        ‘id‘ => 3, 
        ‘name‘ => ‘smarty‘, 
        ‘parentid‘ => 2 
    ), 
    array( 
        ‘id‘ => 4, 
        ‘name‘ => ‘life‘, 
        ‘parentid‘ => 0 
    ), 
    array( 
        ‘id‘ => 5, 
        ‘name‘ => ‘pdo‘, 
        ‘parentid‘ => 2 
    ), 
    array( 
        ‘id‘ => 6, 
        ‘name‘ => ‘pdo-mysql‘, 
        ‘parentid‘ => 5 
    ), 
    array( 
        ‘id‘ => 7, 
        ‘name‘ => ‘java‘, 
        ‘parentid‘ => 1 
    ) 
  );
  //无限极分类
  function tree($arr, $pid, $tmp){
    $tmp=$tmp."&nbsp;&nbsp;";
    for($i=0; $i<count($arr); $i++){
      if($arr[$i]["parentid"]==$pid){
        echo $tmp."|--<a href=".$arr[$i]["id"].">".$arr[$i]["name"]."</a><br/>";
        tree($arr, $arr[$i]["id"], $tmp);
      }
    }
  }
  tree($rows, ‘0‘, ‘‘);

?>

<?php
$categories = array(
    array(‘id‘=>1,‘name‘=>‘电脑‘,‘pid‘=>0),
    array(‘id‘=>2,‘name‘=>‘手机‘,‘pid‘=>0),
    array(‘id‘=>3,‘name‘=>‘笔记本‘,‘pid‘=>1),
    array(‘id‘=>4,‘name‘=>‘台式机‘,‘pid‘=>1),
    array(‘id‘=>5,‘name‘=>‘智能机‘,‘pid‘=>2),
    array(‘id‘=>6,‘name‘=>‘功能机‘,‘pid‘=>2),
    array(‘id‘=>7,‘name‘=>‘超级本‘,‘pid‘=>3),
    array(‘id‘=>8,‘name‘=>‘游戏本‘,‘pid‘=>3),
    array(‘id‘=>9,‘name‘=>‘普通台式机‘,‘pid‘=>4),
    array(‘id‘=>10,‘name‘=>‘高级台式机‘,‘pid‘=>4)
);
$tree = array();
//第一步，将分类id作为数组key,并创建children单元
foreach($categories as $category){
    $tree[$category[‘id‘]] = $category;
    $tree[$category[‘id‘]][‘children‘] = array();
}
//第二部，利用引用，将每个分类添加到父类children数组中，这样一次遍历即可形成树形结构。
foreach ($tree as $k=>$item) {
    if ($item[‘pid‘] != 0) {
        $tree[$item[‘pid‘]][‘children‘][] = &$tree[$k];
    }
}
echo ‘<pre>‘;
print_r($tree);
?>