PDO捕获PDOException构建失败 [英] PDO catch PDOException fails on construction

问题描述

我已经看到这个代码的变化，包括许多S.O。帖子：

I've seen variations of this code all over the place, including many S.O. posts:

class db extends PDO {

    public function __construct( $dbconf ) {
        $options = array(
            PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8',
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_PERSISTENT => $dbconf['persist'] ? true : false
            );
        try {
            parent::__construct('mysql:host='. $dbconf['dbhost'] .';port=3306;dbname='. $dbconf['dbname'] .';' , $dbconf['dbuser'],
                $dbconf['dbpass'],
                $options);
        } catch (PDOException $e) {
            $this->myerror( $e->getMessage() );
            // echo 'Connection failed ... '. $e->getMessage();
        }
    }

    ...

    private function myerror( $error ) {
        echo 'Connection failed ... '. $error;
    }

}

类实例化为 $ db = new db（$ config）; ，如果连接有效，它工作的很好，但看起来 PDOException 如果连接失败，实际工作。 catch 完全无法执行 $ this-> myerror（...） function！而不是有用的 $ e-> getMessage（）说连接失败...访问被拒绝用户blah，我得到一个 PHP致命错误：在第16行上的/.../lib/pdo.class.php中的非对象上调用成员函数myerror（）。

The class is instantiated with $db = new db( $config );, and it works great if the connection is valid, but it seems PDOException doesn't actually work if the connection fails. The catch totally fails to execute the $this->myerror(...) function! Instead of the useful $e->getMessage() that says "Connection failed ... Access denied for user blah", I get a PHP Fatal error: Call to a member function myerror() on a non-object in /.../lib/pdo.class.php on line 16.

如果我注释掉catch中的第一行并取消注释 echo ，它会按预期工作，报告连接错误的原因。为什么消息在catch中可用，但不在简单的 myerror 类函数中？

If I comment out the first line in the catch and uncomment the echo, it works as expected, reporting the reason for the connection error. Why would the message be available in the catch but not in the simple myerror class function?

。 PHP，PDO和例外似乎适用，但没有解释多少。在某些情况下是 catch（PDOException $ e）是否过时或功能不正常？

This post ... PHP, PDO, and Exceptions ... seems applicable, but doesn't explain much. Is catch (PDOException $e) obsolete, or dysfunctional under certain circumstances? How do I keep get this to work?

推荐答案

原因是 PDO :: __ construct

The reason being is PDO::__construct only creates the object upon successful connection. So when you call the parent constructor and it fails your object doesn't exist anymore. You should use self::myerror() to access the error function statically in this case.

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