<?php
 try {
  $dsn = "mysql:host=localhost; port=3306; dbname=wsq_hotel; charset=utf-8";
  $user = 'root';
  $psw ='root';
  $pdo = new PDO($dsn,$user,$psw);
  $sql = 'select goods_prices from wsq_goods_info where goods_id=2';
  // $sql = "show database";
  $res = $pdo->query($sql) or var_dump($pdo->errorInfo());
  // var_dump($res);
  $mon = $res->fetch(PDO::FETCH_ASSOC);
  echo $mon['goods_price'];
 } catch (PDOException $e) {
  echo $e->getMessage();
 }
?>

//开启事务
beginTransacition()
//回滚
rollback()
//提交
commit()
//判断是否处于事务之中
inTransaction()

PDO::lastInsertID()

$sql = "insert into table values('$val')";
if(false===$pdo->exec($sql)){
 echo '执行失败';
}

$pdoStatement = $pdo->prepare(sql结构)

$pdoStatement ->bindValue()

$pdoStatement ->execute()
//$sql = "insert into table values(null,?)";
$sql = "insert into table values(null,:name)";
$stmt = $pdo->prepare($sql);
//多组数据也是一编译一执行
//$stmt->bindValue(1,'bee');
$stmt->bindValue(':name','bee');
$res = $stmt->execute();
var_dump($res);

<?php
header('content-type:text/html;charset=utf-8');
 class PDODB{
  static private $_init;
  private $_host;
  private $_port;
  private $_dbname;
  private $_username;
  private $_password;
  private $_charset;
  private $_dns;
  private $_pdo;
  private function __construct($config){
   $this->_initParamas($config);
   $this->_initDNS();
   $this->_initDriverOptions();
   $this->_initPDO();
  }
  private function __clone(){}
  static public function getInstance($config){
   if(!static::$_init instanceof static){
    static::$_init = new static($config);
   }
   return static::$_init;
  }
  private function _initParamas($config){
   $this->_host = isset($config['host'])?$config['host']:'localhost';
   $this->_port = isset($config['port'])?$config['port']:'3306';
   $this->_dbname = isset($config['dbname'])?$config['dbname']:'';
   $this->_username = isset($config['username'])?$config['username']:'root';
   $this->_passward = isset($config['passward'])?$config['passward']:'';
   $this->_charset = isset($config['charset'])?$config['charset']:'utf8';
  }
  private function _initDNS(){
   $this->_dns = "mysql:host=$this->_host;port=$this->_port;dbname=$this->_dbname";
  }
  private function _initDriverOptions(){
   $this->_driverOptions = array(
    PDO::MYSQL_ATTR_INIT_COMMAND => "set names $this->_charset"
   );
  }
  private function _initPDO(){
   $this->_pdo = new PDO($this->_dns,$this->_username,$this->_passward,$this->_driverOptions) or die("fail");
  }
  public function query($sql){
   if(!$result = $this->_pdo->query($sql)){
    $erro = $this->_pdo->errorInfo();
    echo '失败的语句'.$sql.'<br>';
    echo '错误代码'.$erro[1].'<br>';
    echo '错误信息'.$erro[2].'<br>';
    die;
   }
   return $result;
  }
  public function fetchAll($sql){
   $res = $this->query($sql);
   $list = $res->fetchAll(PDO::FETCH_ASSOC);
   $res->closeCursor();
   return $list;
  }
  public function fetchRow($sql){
   $res = $this->query($sql);
   $row = $res->fetch(PDO::FETCH_ASSOC);
   $res->closeCursor();
   return $row;
  }
  public function fetchOne($sql){
   $res = $this->query($sql);
   $one = $res->fetchColumn();
   $res->closeCursor();
   return $one;
  }
  public function escape_string($data){
   return $this->_pdo->quote($data);
  }
 }
 $config = array(
  "host"=>"localhost",
  "username"=>"root",
  "passward"=>"root",
  "dbname"=>"students"
 );
 $pdo = PDODB::getInstance($config);
 $sql = "select sdept from student where sage=21";
 var_dump($pdo->fetchRow($sql));
?>