PHP尝试/捕获和致命错误 [英] PHP try/catch and fatal error

问题描述

我正在使用以下脚本通过PHP使用数据库:

I'm using the following script to use a database using PHP:

try{
    $db = new PDO('mysql:host='.$host.';port='.$port.';dbname='.$db, $user, $pass, $options);
}
catch(Exception $e){
    $GLOBALS['errors'][] = $e;
}

现在，我想使用此数据库句柄使用以下代码进行请求:

Now, I want to use this database handle to do a request using this code:

try{
    $query = $db->prepare("INSERT INTO users (...) VALUES (...);");
    $query->execute(array(
        '...' => $...,
        '...' => $...
    ));
}
catch(Exception $e){
    $GLOBALS['errors'][] = $e;
}

问题出在这里

• 与数据库的连接正常后，一切正常，
• 当连接失败但我不使用数据库时，我拥有$GLOBALS['errors'][]数组，此后脚本仍在运行，
• 与数据库的连接失败时，出现以下致命错误:

• When the connection to the DB is OK, everything works,
• When the connection fails but I don't use the DB, I have the $GLOBALS['errors'][] array and the script is still running afterwards,
• When the connection to the DB has failed, I get the following fatal error:

注意:未定义的变量:第32行的C:\ xampp \ htdocs [...] \ test.php中的数据库

Notice: Undefined variable: db in C:\xampp\htdocs[...]\test.php on line 32

致命错误:在第32行的C:\ xampp \ htdocs [...] \ test.php中的非对象上调用成员函数prepare()

Fatal error: Call to a member function prepare() on a non-object in C:\xampp\htdocs[...]\test.php on line 32

注意:第32行是$query = $db->prepare(...)指令.

也就是说，脚本崩溃了，并且try/catch似乎没有用.您知道为什么第二次尝试/捕获不起作用以及如何解决吗?

That is to say, the script crashes, and the try/catch seems to be useless. Do you know why this second try/catch don't works and how to solve it?

感谢您的帮助！

编辑:有一些非常好的答复.我已经验证了一种不完全是我想要做的方法，但这可能是最好的方法.

There are some really good replies. I've validated one which is not exactly what I wanted to do, but which is probably the best approach.

推荐答案

try/catch块仅适用于抛出的异常(必须调用throw Exception或Exception的子类).您无法使用try/catch捕获致命错误.

try/catch blocks only work for thrown exceptions (throw Exception or a subclass of Exception must be called). You cannot catch fatal errors using try/catch.

如果无法建立数据库连接，我认为这是致命的，因为您可能需要数据库来执行页面上有意义的任何事情.

If your DB connection cannot be established, I would consider it fatal since you probably need your DB to do anything meaningful on the page.

PDO将引发异常.您的特定问题是，当尝试使用$db调用方法时未定义它，因此您会得到致命的空指针(某种).而不是像其他人所建议的那样跳过if ($db == null)箍，您应该修复代码以确保在需要时始终定义$db，或者采用不太脆弱的方式来确保数据库连接可用.使用它的代码.

PDO will throw an exception if the connection cannot be established. Your specific problem is that $db is not defined when you try to call a method with it so you get a null pointer (sort of) which is fatal. Rather than jump through if ($db == null) hoops as others are suggesting, you should just fix your code to make sure that $db is either always defined when you need it or have a less fragile way of making sure a DB connection is available in the code that uses it.

如果您真的想捕获"致命错误，请使用set_error_handler，但这仍然会在发生致命错误时停止脚本执行.

If you really want to "catch" fatal errors, use set_error_handler, but this still stops script execution on fatal errors.

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