封装PDO连接数据库代码

废话不说直接上代码：

 <?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;
     }
 }
 ?>

如何使用：

<?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
?>