<?php

 class DB

 {

     protected static $_connect;

     protected $dsn, $pdo;

     protected $_data, $_count, $_lastInsertId;

     /**

      * 构造函数

      *

      * @return DB

      */

     private function __construct($dbHost, $dbUser, $dbPasswd, $dbName, $dbCharset, $dbms)

     {

         try {

             $this->dsn = $dbms.':host='.$dbHost.';dbname='.$dbName;

             $this->pdo = new PDO($this->dsn, $dbUser, $dbPasswd);

             $this->pdo->exec('SET character_set_connection='.$dbCharset.', character_set_results='.$dbCharset.', character_set_client=binary');

         } catch (PDOException $e) {

             $this->outputError($e->getMessage());

         }

     }

     /**

      * 获取返回结果、行数及最新插入数据的id

      *

      */

     public function data(){

         return $this->_data;

     }

     public function count(){

         return $this->_count;

     }

     public function lastInsertId(){

         return $this->_lastInsertId;

     }

     /**

      * 防止克隆

      *

      */

     private function __clone() {}

     /**

      * Singleton instance

      *

      * @return Object

      */

     public static function connect($dbHost, $dbUser, $dbPasswd, $dbName, $dbCharset="utf8", $dbms="mysql")

     {

         if (self::$_connect === null) {

             self::$_connect = new self($dbHost, $dbUser, $dbPasswd, $dbName, $dbCharset, $dbms);

         }

         return self::$_connect;

     }

     /**

      * Go 增删改查覆盖

      *

      * @param String $strSql SQL语句

      * @param Array $arrayInputValue 替换占位符的值

      * @return Object

      */

     public function go($strSql, $arrayInputValue){

         $handle=strtolower(preg_split("/\s+/",$strSql)[0]);//----获取sql语句第一个词（可能是select、update、delete、insert或replace）

         if(strpos("/insert/delete/update/select/replace",$handle)>0){

             $stmt = $this->pdo->prepare($strSql);

             $stmt->execute($arrayInputValue);

             $this->getPDOError();

             $this->_data = $stmt->fetchAll(PDO::FETCH_ASSOC);

             $this->_count=$stmt->rowCount();// ----如果是覆盖旧数据，rowCount不准确

             $this->_lastInsertId=$this->pdo->lastInsertId();

             return $this;

         }else{

             echo "<br>请检查sql语句是否有误！<br>";

         }

     }

     /**

      * execSql

      *

      * @param String $strSql

      * @return Int

      */

     public function execSql($strSql)

     {

         $result = $this->pdo->exec($strSql);

         $this->getPDOError();

         return $result;

     }

     /**

      * 获取字段最大值

      *

      * @param string $table 表名

      * @param string $field_name 字段名

      * @param string $where 条件

      */

     public function getMaxValue($table, $field_name, $where = '')

     {

         $strSql = "SELECT MAX(".$field_name.") AS MAX_VALUE FROM $table";

         if ($where != '') $strSql .= " WHERE $where";

         $stmt = $this->pdo->prepare($strSql);

         $stmt->execute();

         $data = $stmt->fetchAll(PDO::FETCH_ASSOC);

         $maxValue = $data[0]["MAX_VALUE"];

         if ($maxValue == "" || $maxValue == null) {

             $maxValue = 0;

         }

         return $maxValue;

     }

     /**

      * 获取指定列的数量

      *

      * @param string $table

      * @param string $field_name

      * @param string $where

      * @return int

      */

     public function getCount($table, $field_name, $where = '')

     {

         $strSql = "SELECT COUNT($field_name) AS NUM FROM $table";

         if ($where != '') $strSql .= " WHERE $where";

         $stmt = $this->pdo->prepare($strSql);

         $stmt->execute();

         $data = $stmt->fetchAll(PDO::FETCH_ASSOC);

         return $data[0]["NUM"];

     }

     /**

      * 获取指定列的总和

      *

      * @param string $table

      * @param string $field_name

      * @param string $where

      * @return int

      */

     public function getSum($table, $field_name, $where = '')

     {

         $strSql = "SELECT SUM($field_name) AS SN FROM $table";

         if ($where != '') $strSql .= " WHERE $where";

         $stmt = $this->pdo->prepare($strSql);

         $stmt->execute();

         $data = $stmt->fetchAll(PDO::FETCH_ASSOC);

         return $data[0]["SN"];

     }

     /**

    * 预处理执行

    */

     public function prepareSql($sql=''){

         return $this->pdo->prepare($sql);

   }

     /**

    * 执行预处理

    */

     public function execute($presql){

         return $this->pdo->execute($presql);

     }

     /**

      * pdo属性设置

      */

     public function setAttribute($p,$d){

         $this->pdo->setAttribute($p,$d);

     }

     /**

      * beginTransaction 事务开始

      */

     public function beginTransaction()

     {

         $this->pdo->beginTransaction();

     }

     /**

      * commit 事务提交

      */

     public function commit()

     {

         $this->pdo->commit();

     }

     /**

      * rollback 事务回滚

      */

     public function rollback()

     {

         $this->pdo->rollback();

     }

     /**

      * getPDOError 捕获PDO错误信息

      */

     private function getPDOError()

     {

         if ($this->pdo->errorCode() != '00000') {

             $arrayError = $this->pdo->errorInfo();

             $this->outputError($arrayError[2]);

         }

     }

     /**

      * 输出错误信息

      *

      * @param String $strErrMsg

      */

     private function outputError($strErrMsg)

     {

         throw new Exception('MySQL Error: '.$strErrMsg);

     }

     /**

      * 关闭数据库连接

      */

     public function close()

     {

         $this->pdo = null;

     }

 }

 ?>

<?php

require "db.class.php";//----引入文件

$pdo=DB::connect("localhost","root","[密码]","[数据库名]");//--创建PDO并连接数据库

$sql="……";//----注：这里sql语句占位符必须用“?”表示

$pdo->go($sql, array("[value1]","[value2]",...));//---执行sql语句(所有sql语句均可用go函数执行)

var_dump($pdo->result());//----打印结果集（如果是select语句返回的是代表结果集的数组，如果是其他语句返回的是空数组）

echo $pdo->count();//-----如果是select打印的是结果集包含的数据数量，如果是delete或update打印的是删除或更改的数据数量

echo $pdo->lastInsertId();//------如果是insert语句，$pdo->lastInsertId()表示最新插入数据的id

$pdo->close();//----关闭连接

?>