如果你是喷子，问我造轮子花这么多精力有什么用的话，那就走，看看我的这篇文章 为什么我要写自己的框架？框架所有的代码都在笔者的Github上做展示，并且有一个库存管理信息系统的实例，Github账号请看笔者简介
这是自编写框架的第一篇，之后计划写路由篇、小组件篇、工厂篇等
数据库操作可以说是网页应用程序的核心，他直接决定了你的程序是干什么的看大标题，很明显的发现这是一篇和PDO封装有关系的文章，再一次感谢Yii2.0框架给我设计模式方面的启发。废话不多说，我们开始
封装分为两个类：Connection类 | Command类
首先，作为PHP，一个请求就会对应一个PHP线程，在这个大环境下，一个线程有多个数据库连接岂不是很浪费，因此，我运用单例模式让请求的整个生命周期内共享数据库连接
//Connection类private static $_instance;private function __construct() {}private function __clone() {}//单例public static function getinstance() { if (!(self::$_instance instanceof self)) { self::$_instance = new self(); } return self::$_instance;}//类被回收的时候调用，此时关闭数据库连接public function __destruct() { $this->close();}有了单例模式之后我们就需要进行实际的连接数据库操作了通过config配置数据库，运用PDO独特的语法dsn：
return [ 'dsn' => 'mysql:host=127.0.0.1;dbname=dbname', 'user' => 'root', 'password' => 'pass', 'charset' => 'utf8', 'slaves' => [ [ 'dsn' => 'mysql:host=127.0.0.1;dbname=dbname', 'user' => 'root', 'password' => 'pass', 'charset' => 'utf8', ], ],];
下面这些是Connection的变量，这个设计把从服务器所有的连接实例化都储存在一个私有变量中，统一进行管理
//实例化后数据库连接属性public $connect;private $db; //数据库连接信息//服务器信息，私有属性private $dsn;private $user;private $pass;private $charset;private $rightNowDb; //当前服务器信息私有属性的服务器名private $PDOSlaves; //从服务器实例化后数据库连接属性
获取数据库连接信息，一旦信息不完整
private function getInfo() { $this->db = require (dirname(__FILE__).'/../../config/db.php'); if ($this->db['dsn'] && $this->db['user'] && $this->db['password']) { $this->dsn = $this->db['dsn']; $this->user = $this->db['user']; $this->pass = $this->db['password']; $this->charset = $this->db['charset']?$this->db['charset']:'utf8'; $this->rightNowDb = 'master'; } else { $this->err('One of the PDO::DB Parameter is empty!'); }}private function err($err) { $err = 'ErrInfo: '.$err; LogWrite::getinstance()->IntoWhere('errordb')->Info($err)->execute(); throw new Exception($err);}PDO连接方法，这就是PDO的连接方法，运用new PDO进行操作
private function nowConnect() { try { $connect = new PDO($this->dsn, $this->user, $this->pass); } catch (PDOException $e) { $this->err($e->getMessage()); } if (!$connect) { $this->err('PDO connect error'); } $connect->exec('SET NAMES '.$this->charset); $connect->getAttribute(constant("PDO::ATTR_SERVER_VERSION")); return $connect;}数据库关闭、数据库是否活跃方法(简单，直接贴代码，不做解释)
public function getConnect() { $this->getInfo(); if ($this->isActive()) { return $this->connect; } else { $this->connect = $this->nowConnect(); return $this->connect; }}//if there is activepublic function isActive() { return $this->connect;}//close connectionpublic function close() { if ($this->isActive()) { $this->connect = null; }}下面就到了我们实际使用数据库连接的方法了，如果程序员使用到数据库连接，这些方法是最常用的，那就是获取连接
public function getConnect() { $this->getInfo(); if ($this->isActive()) { return $this->connect; } else { $this->connect = $this->nowConnect(); return $this->connect; }}下面就是从服务器连接的代码
public function getSlavesConnect($num) { $this->setToSlaves($num); $key = 'slave'.$num; if ($this->PDOSlaves[$key]) { return $this->PDOSlaves[$key]; } else { $connect = $this->nowConnect(); $this->PDOSlaves[$key] = $connect; return $this->PDOSlaves[$key]; }}//Serval attributes change to slaver DataBasepublic function setToSlaves($num) { if ($this->db['slaves'][$num]['dsn'] && $this->db['slaves'][$num]['user'] && $this->db['slaves'][$num]['password']) { $this->dsn = $this->db['slaves'][$num]['dsn']; $this->user = $this->db['slaves'][$num]['user']; $this->pass = $this->db['slaves'][$num]['password']; $this->rightNowDb = 'slaves'.$num; } else { $this->err('slaves '.$num.':: missing info!'); }}public function setMaster() { $this->getInfo(); return $this;}public function getRightNowDb() { return $this->rightNowDb;}写到这边很多人就有疑问了，介绍了这么多方法，都是数据库连接的，光连接数据库没有什么用处啊！还是不对数据库做一点的操作，而且按照现在的介绍应该会new两个类，进行互不相干的联系，这样不是很low！还不如封装成一个！
有这个想法的人很好！说明在思考，因为我当时在阅读Yii2.0源码的时候打开它也有这同样的想法，但之后看到了他对这个的解决方法，我茅塞顿开
public function createCommand($sql = null) { //first connect the db $command = new Command([ 'db' => $this->getConnect(), 'sql' => $sql, ]); return $command;}public function createSlavesComm($num = 0, $sql = null) { $command = new Command([ 'db' => $this->getSlavesConnect($num), 'sql' => $sql, ]); return $command;}这就是所有的数据库连接的代码，下面介绍Command类，首先是构造方法和一些属性，数据库连接很显然就储存在类内pdo的属性内
//this save sql wordprivate $sql;//pdo connectprivate $pdo;//the pdo statementprivate $pdoStmt;//the last db select is in hereprivate $lastCommandDb;private $dataType = PDO::FETCH_ASSOC; //从数据库内取出数据的默认属性//Connection.php to new a commandpublic function __construct($arr) { $this->sql = $arr['sql']?$arr['sql']:''; $this->pdo = $arr['db'];}数据库sql搜索，分为准备和执行两步，运用PDO的方法，一旦有错误，抛错，记录日志，没有准备就执行的话，系统会抛throw new PDOException('PDO is Fail to use execute before prepare!');错误
//Must handleprivate function prepare() { //if there have stmt if ($this->pdoStmt) { $this->lastCommandDb = $this->pdoStmt; } $this->pdoStmt = $this->pdo->prepare($this->sql);}//execute it and returnprivate function execute($method) { if ($this->pdoStmt) { $pdoStmt = $this->pdoStmt; $pdoStmt->execute(); $res = $pdoStmt->$method($this->dataType); if (!$res) { $msg = 'The result is empty, The sql word is :: '.$this->sql; LogWrite::getinstance()->IntoWhere('errordb')->Info($msg)->execute(); return false; } return $res; } else { throw new PDOException('PDO is Fail to use execute before prepare!'); }}下面介绍事务，作为一个数据库操作，那就肯定需要事务，没有事务的话，往往就出现致命的错误，突然说到事务有可能会有点唐突，下面就举个很简单的例子，关于银行的
银行内部不同的人会对应不同的账户，每个账户都是一条数据库记录，下面模拟一个转账业务：A转账给B 100块
当A转账给B的时候，A账户内的钱减去100，此时是成功的，当给B内的帐户添加100块的时候，由于某些原因（由于死锁导致执行时间超时，系统内部错误等），B的帐户内没有多100块钱，这个转账事务其实是失败的，但是一旦没有事务的约束，只有拋个错，没有纪录和回滚的话其实对于一个转账业务来说这是致命的！！！！
在这个基础上，就诞生了事务的概念，PDO也有对其的一套完整的解决方案，那我们下面就来封装它
//transction handleprivate function transction() { try { $this->pdo->beginTransaction(); $res = $this->pdo->exec($this->sql); if ($this->pdo->errorInfo()[0] != '00000') { throw new PDOException('DB Error::Fail to change the database!! The sql is: '.$this->sql.' The Error is :: '.$this->pdo->errorInfo()[2]); } $this->pdo->commit(); return true; } catch (PDOException $e) { $this->pdo->rollback(); LogWrite::getinstance()->IntoWhere('errordb')->Info($e)->execute(); return false; }}//change it latelyprivate function transctions(array $sqlArr = array()) { try { $this->pdo->beginTransaction(); foreach ($sqlArr as $value) { $res = $this->pdo->exec($value); print_r($this->pdo->errorInfo()); if ($this->pdo->errorInfo()[0] != '00000') { throw new PDOException('DB Error::Fail to change the database!! The sql is: '.$value.' The Error is :: '.$this->pdo->errorInfo()[2]); } } $this->pdo->commit(); return true; } catch (PDOException $e) { $this->pdo->rollback(); LogWrite::getinstance()->IntoWhere('errordb')->Info($e)->execute(); return false; }}以上就是基础的一些方法的封装，那应该如何使用这些方法呐，当然就是增删改查咯！
public function queryAll($fetchMode = null) { return $this->queryInit('fetchAll', $fetchMode);}public function queryOne($fetchMode = null) { return $this->queryInit('fetch', $fetchMode);}//insert into databasepublic function insert($table, $arr) { $this->sql = Merj::sql()->insert($table)->value($arr)->sqlVal(); return $this->transction();}//insert serval databasepublic function insertSomeVal($table, array $key, array $arr) { $this->sql = Merj::sql()->insert($table)->servalValue($key, $arr)->sqlVal(); return $this->transction();}//update the databasepublic function update($table, $arr, $where) { $this->sql = Merj::sql()->update($table)->set($arr)->where($where)->sqlVal(); return $this->transction();}public function updateTrans(array $sqlArr = array()) { return $this->transctions($sqlArr);}//delete one recordpublic function delete($table, $whereArr) { $this->sql = Merj::sql()->delete($table)->where($whereArr)->sqlVal(); return $this->transction();}private function queryInit($method, $fetchMode = null) { if ($fetchMode) { $this->dataType = $fetchMode; } if ($this->sql && $this->pdo) { $this->prepare(); $result = $this->execute($method); return $result?$result:''; } else { $err = 'Sql or PDO is empty; The sql is '.$this->sql; LogWrite::getinstance()->IntoWhere('errordb')->Info($this->sql)->execute(); throw new PDOException($err); return false; }}方法很多，其实是有规律的
public static function sql() { return new QueryBuilder();}$connect = Connection::getinstance();$connect->createCommand($sql)->queryOne();$connect->createCommand($sql)->queryAll();$connect::db()->createCommand()->insert('tableName', [ 'Val Key1' => 'Val1', 'Val Key2' => 'Val2', ]);Merj::db()->createSlavesComm(0, 'SELECT * FROM content')->queryAll(); //从服务器操作数据库数据库的模型类方法部分展示，所有模型继承至此类：
/** * 返回一条纪录内的一个值 * @param 想要取出的值 * @param 主键对应的值 * @return 返回一个值 **/public function findOnlyOne($target, $idVal) { $sql = Merj::sql()->select($target)->from($this->tableName)->where([ $this->primKey => $idVal, ])->sqlVal(); $rows = Merj::db()->createCommand($sql)->queryOne(); if ($rows) { return $rows[$target]; } else { return false; }}/** * 返回一条纪录 * @param 主键属性 * @param 主键对应的值 * @return 返回这条纪录 **/public function findOneRecord($userIdVal) { $sql = Merj::sql()->select()->from($this->tableName)->where([ $this->primKey => $userIdVal, ])->sqlVal(); $rows = Merj::db()->createCommand($sql)->queryOne(); if ($rows) { return $rows; } else { return false; }}/** * 通过sql语句查找 * @param sql words * @return results **/public function findBySql($sql) { return Merj::db()->createCommand($sql)->queryAll();}/** * @param Insert info * @return success or not **/ public function insertOne($arr) { return Merj::db()->createCommand()->insert($this->tableName, $arr);}/** * @param Insert infos * @return success or not **/public function insertNum(array $key = array(), array $arr = array()) { return Merj::db()->createCommand()->insertSomeVal($this->tableName, $key, $arr);}/** * 更新一条记录 * @param * @param * @return success or not **/public function updateOneRec($arrUpDate, $idVal) { return Merj::db()->createCommand()->update($this->tableName, $arrUpDate, [ $this->primKey => $idVal, ]);}/** * 多个sql语句更新 * @param sql array * @return success or not **/public function updateTrans($sqlArr) { return Merj::db()->createCommand()->updateTrans($sqlArr);}/** * 删除一条记录 * @param where $arr * @return success or not **/public function deleteOne($arr) { return Merj::db()->createCommand()->delete($this->tableName, $arr);}/** * object to array * @param object * @return array **/public function obj_arr($obj) { if (is_object($obj)) { $array = (array) $obj; }if (is_array($obj)) { foreach ($obj as $key => $value) { $array[$key] = $this->obj_arr($value); } } return $array;}public function jsonUtf8Out($arr) { foreach ($arr as $key => $value) { if (is_array($value)) { $arr[$key] = $this->jsonUtf8Out($value); } else { $arr[$key] = urlencode($value); } } return $arr;}最后两个方法为两个递归方法
好了！说了这么多，笔者要去吃饭了！明天还有一天的高考，祝大家高考顺利！
