PHP连接mysql

$servername = "localhost";   //服务器
$username = "root";     //用户名
$password = "root";    //密码
$dbname="base";　　　　//表名
$params = array (
    PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES \'UTF8\'' ,   //设置字符集 保证中文不乱码
    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,           //设置当前pdo的错误处理方式
);
try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password, $params);
    echo "连接成功";

    //查询
    $sqlinquire = 'select * from shop';
//    $sqlinquire = 'select * from shop WHERE Id=3||typeId=1';//给查询加入限制条件
    $preinquire = $conn->prepare($sqlinquire);
    $preinquire->execute();
    $resultinquire=$preinquire->fetchAll(PDO::FETCH_ASSOC);



    //插入，增加记录
    $str='';
    $arr=array();
    for($i=0;$i<10;$i++){
        if($i==0){
            $str="(?,?,?)";
        }else{
            $str.=",(?,?,?)";
        }
        $s="张三".rand(1000,100000);
        $t=rand(1,3);
        $m='￥'.rand(100,1000);
        $arr[]=$s;
        $arr[]=$t;
        $arr[]=$m;
    }
    echo $str;
    print_r($arr);
    $sqladd="INSERT INTO shop(shopname,typeId,money) VALUES $str";
    $preadd = $conn->prepare($sqladd);
    $preadd->execute($arr);



    //修改编辑数据
    $sqlchange="UPDATE shop SET money='￥1599' WHERE Id=2";
    $prechange = $conn->prepare($sqlchange);
    $prechange->execute();

    //删除
    $sqldel="DELETE FROM shop";
    $predel = $conn->prepare($sqldel);
    $predel->execute();

} catch(PDOException $e) {
    echo $e->getMessage();
}