PHP PDO数据库操作预处理与注意事项

<?php
header('content-type:text/html; charset=utf-8');
//实例化pdo对象
$pdo = new PDO('mysql:host=127.0.0.1;port=3306;dbname=test;', 'root', '888888');
//通过query函数执行sql命令
$pdo->query('set names utf8');
//插入数据
$sql  = "insert into persons (name,age) values (?, ?);";
$preObj = $pdo->prepare($sql);
$res  = $preObj->execute(array('小明', 22));
var_dump($res);
//删除数据
$sql = "delete from persons where id = ?";
$preObj = $pdo->prepare($sql);
$res  = $preObj->execute(array(3));
var_dump($res);
//修改数据
$sql = "update persons set name = ? where id = ?;";
$preObj = $pdo->prepare($sql);
$res  = $preObj->execute(array('lucy', 5));
var_dump($res);
//查询数据
$sql = "select * from persons where age > ? order by id desc;";
$preObj = $pdo->prepare($sql);
$preObj->execute(array(20));
$arr = $preObj->fetchAll(PDO::FETCH_ASSOC);
/*
 * FETCH_BOTH   是默认的，可省，返回关联和索引。
 * FETCH_ASSOC   参数决定返回的只有关联数组。
 * PDO::FETCH_NUM 返回索引数组
 * PDO::FETCH_OBJ 返回由对象组成的二维数组
 */
print_r($arr);

<?php
$dsn = 'mysql:dbname=test;host=127.0.0.1';
$user = 'root';
$password = '';
try {
  $dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
  echo 'Connection failed: ' . $e->getMessage();
}
/* Execute a prepared statement by passing an array of values */
$sth = $dbh->prepare('INSERT INTO room (create_time,create_uid,exp_time,is_private) VALUES (?,?,?,?)');
$rs = $sth->execute(["2018-05-14 14:10:04",0,1526278504,1]);
var_dump($sth->errorInfo());exit;