pdo 连接数据库

'DB_DSN'=>'mysql:host=IP;port=3307;dbname=test;charset=utf8',

$db = 10.15.208.206;port=3307

/**
* 连接数据库
*/
public function connect($host, $user, $pass, $db) 
{
   try {
       $this->_resource =new PDO("mysql:dbname=$db;host=$host", $user, $pass);
       return $this->_resource;
   }catch (PDOException $e){
       return null;
   }
   //return null;
}