最简单递归

 public function testAction(){    $arr = [        ['id'=>1,'pid'=>0,'name'=>'PHP'],        ['id'=>2,'pid'=>0,'name'=>'JAVA'],        ['id'=>3,'pid'=>0,'name'=>'Mysql'],        ['id'=>4,'pid'=>1,'name'=>'php类'],        ['id'=>5,'pid'=>1,'name'=>'echo方法'],        ['id'=>6,'pid'=>2,'name'=>'java类'],        ['id'=>7,'pid'=>3,'name'=>'select方法'],        ['id'=>8,'pid'=>4,'name'=>'php实例'],        ['id'=>9,'pid'=>8,'name'=>'php实例儿子'],    ];        print_r($this->tree($arr,1));}    private function tree(&$arr,$pid=0){        static $tree=array();        foreach($arr as $v){            if($v['pid']==$pid){                $tree[]=$v;                $this->tree($arr,$v['id']);            }        }        return $tree;    }