我使用PHP 7.1.23测试了以下代码：

$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES,true);

$sth = $pdo->prepare('select now() and this is a bad sql where a - b from c');

if ($sth === false) {

echo "error on prepare()\n";

print_r($pdo->errorInfo());

}

if ($sth->execute() === false) {

echo "error on execute()\n";

print_r($sth->errorInfo());

}

error on execute()

Array

(

[0] => 42000

[1] => 1064

[2] => You have an error in your sql Syntax; check the manual that corresponds to your MysqL server version for the right Syntax to use near 'a bad sql where a - b from c' at line 1

)

然后,我测试了相同的代码,除非禁用了仿真的prepare：

$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES,false);

error on prepare()

Array

(

[0] => 42000

[1] => 1064

[2] => You have an error in your sql Syntax; check the manual that corresponds to your MysqL server version for the right Syntax to use near 'a bad sql where a - b from c' at line 1

)

Fatal error: Uncaught Error: Call to a member function execute() on boolean

故事的道德启示：

>使用模拟的准备好的语句时,prepare()是空操作,并且错误会延迟到execute()为止.我建议禁用模拟的prepare,除非您使用的数据库不支持prepared语句(我不知道任何RDBMS产品的任何当前版本都不能执行真正的prepared语句).

>在prepare()上检查错误时,请使用$pdo-> errorInfo().

>在execute()上检查错误时,请使用$stmt-> errorInfo().