php 封装PDO类

<?php//数据库连接类，不建议直接使用DB，而是对DB封装一层//这个类不会被污染，不会被直接调用class DB {//pdo对象private $_pdo = null;//用于存放实例化的对象static private $_instance = null;//公共静态方法获取实例化的对象static protected function getInstance() {if (!(self::$_instance instanceof self)) {self::$_instance = new self();}return self::$_instance;}//私有克隆private function __clone() {}//私有构造private function __construct() {try {$this->_pdo = new PDO(DB_DNS, DB_USER, DB_PASS, array(PDO::MYSQL_ATTR_INIT_COMMAND=>'SET NAMES '.DB_CHARSET));$this->_pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);} catch (PDOException $e) {exit($e->getMessage());}}//新增protected function add($_tables, Array $_addData) {$_addFields = array();$_addValues = array();foreach ($_addData as $_key=>$_value) {$_addFields[] = $_key;$_addValues[] = $_value;}$_addFields = implode(',', $_addFields);$_addValues = implode("','", $_addValues);$_sql = "INSERT INTO $_tables[0] ($_addFields) VALUES ('$_addValues')";return $this->execute($_sql)->rowCount();}//修改protected function update($_tables, Array $_param, Array $_updateData) {$_where = $_setData = '';foreach ($_param as $_key=>$_value) {$_where .= $_value.' AND ';}$_where = 'WHERE '.substr($_where, 0, -4);foreach ($_updateData as $_key=>$_value) {if (Validate::isArray($_value)) {$_setData .= "$_key=$_value[0],";} else {$_setData .= "$_key='$_value',";}}$_setData = substr($_setData, 0, -1);$_sql = "UPDATE $_tables[0] SET $_setData $_where";return $this->execute($_sql)->rowCount();}//验证一条数据protected function isOne($_tables, Array $_param) {$_where = '';foreach ($_param as $_key=>$_value) {$_where .=$_value.' AND ';}$_where = 'WHERE '.substr($_where, 0, -4);$_sql = "SELECT id FROM $_tables[0] $_where LIMIT 1";return $this->execute($_sql)->rowCount();}//删除protected function delete($_tables, Array $_param) {$_where = '';foreach ($_param as $_key=>$_value) {$_where .= $_value.' AND ';}$_where = 'WHERE '.substr($_where, 0, -4);$_sql = "DELETE FROM $_tables[0] $_where LIMIT 1";return $this->execute($_sql)->rowCount();}//查询protected function select($_tables, Array $_fileld, Array $_param = array()) {$_limit = $_order = $_where = $_like = '';if (Validate::isArray($_param) && !Validate::isNullArray($_param)) {$_limit = isset($_param['limit']) ? 'LIMIT '.$_param['limit'] : '';$_order = isset($_param['order']) ? 'ORDER BY '.$_param['order'] : '';if (isset($_param['where'])) {foreach ($_param['where'] as $_key=>$_value) {$_where .= $_value.' AND ';}$_where = 'WHERE '.substr($_where, 0, -4);}if (isset($_param['like'])) {foreach ($_param['like'] as $_key=>$_value) {$_like = "WHERE $_key LIKE '%$_value%'";}}}$_selectFields = implode(',', $_fileld);$_table = isset($_tables[1]) ? $_tables[0].','.$_tables[1] : $_tables[0];$_sql = "SELECT $_selectFields FROM $_table $_where $_like $_order $_limit";$_stmt = $this->execute($_sql);$_result = array();while (!!$_objs = $_stmt->fetchObject()) {$_result[] = $_objs;}return Tool::setHtmlString($_result);}//总记录protected function total($_tables, Array $_param = array()) {$_where = '';if (isset($_param['where'])) {foreach ($_param['where'] as $_key=>$_value) {$_where .= $_value.' AND ';}$_where = 'WHERE '.substr($_where, 0, -4);}$_sql = "SELECT COUNT(*) as count FROM $_tables[0] $_where";$_stmt = $this->execute($_sql);return $_stmt->fetchObject()->count;}//得到下一个IDprotected function nextId($_tables) {$_sql = "SHOW TABLE STATUS LIKE '$_tables[0]'";$_stmt = $this->execute($_sql);return $_stmt->fetchObject()->Auto_increment;}//执行SQLprivate function execute($_sql) {try {$_stmt = $this->_pdo->prepare($_sql);$_stmt->execute();} catch (PDOException  $e) {exit('SQL语句：'.$_sql.'<br />错误信息：'.$e->getMessage());}return $_stmt;}}?>