<?php
//默认是不提示的 需要用 errorCode() errorInfo();
try{
  $pdo = new PDO("mysql:host=localhost;dbname=jikexueyuan","root","");
  //下面这句是默认设置，有无均可
  $pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_SILENT);
}catch(PDOException $e){
  die("数据库连接失败".$e->getMessage());
}
$sql = "insert into stuu values(null,'jike','w',55)";
$res = $pdo->exec($sql);
if($res){
  echo "OK";
}else{
  echo $pdo->errorCode();
  print_r($pdo->errorInfo());
} 

<?php
try{
  $pdo = new PDO("mysql:host=localhost;dbname=jikexueyuan","root","");
  //主动以警告的形式报错
  $pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_WARNING);
}catch(PDOException $e){
  die("数据库连接失败".$e->getMessage());
}
$sql = "insert into stuu values(null,'jike','w',55)";
//若有错误直接在浏览器页面中显示错误信息
$res = $pdo->exec($sql);

<?php
try{
  $pdo = new PDO("mysql:host=localhost;dbname=jikexueyuan","root","");
  //主动抛出异常
  $pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION );
}catch(PDOException $e){
  die("数据库连接失败".$e->getMessage());
}
$sql = "insert into stuu values(null,'jike','w',55)";
//用try{}catch(){}抓取异常
try{
  $res = $pdo->exec($sql);
}catch(PDOException $e){
  echo $e->getMessage();
}