blocks|key|790148|text|这就是异常的全部意义--你可以有多个不同的catch块来捕捉你想要处理的任何异常。异常的数据必须被赋值到某个地方，因此变量。如果你真的不想看到这些警告，你可以在catch代码块中执行类似unset($e)的操作……或者禁用警告(通常不是一个好主意)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|790149|entityMap^0|2L|9|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

That's the whole point of exceptions - you can have multiple different catch blocks to catch any exceptions you'd want to handle. The exception's data has to be assigned somewhere, hence the variable. You could just do something like <code>unset($e)</code> inside the catch block if you really don't want to see those warnings... or disable the warnings (generally a bad idea).

blocks|key|1744875|text|不是的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1744876|在任何情况下，捕获异常并什么都不做通常是一个坏主意；异常的存在正是为了迫使您处理异常情况(否则执行将中止)，因此可以理解该语言不会促进这样的用例。|1744877|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

No.

In any case, it's generally a bad idea to catch an exception and do nothing; exceptions exist precisely to force you to handle the exceptional circumstance (otherwise execution is aborted), so it's comprehensible the language doesn't facilitate such a use case.

blocks|key|790233|text|异常不仅仅用于异常情况。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|790234|此场景实际上使用异常来确保用户已注销。在脚本中的这一点上，找出哪些数据应该被修剪是非常耗费资源的，所以实际上只修剪所有数据并捕获异常会更快。|790235|++++++++try+{
++++++++GDS::$DB->exec('DELETE+FROM+sessions+WHERE+session_id+=+'+.+session_id());
++++++++GDS::$DB->exec('DELETE+FROM+sessions+WHERE+user_id+=+'+.+$this->data['user_id']);
++++}+catch(PDOException+$ex)+{}
++++session_regenerate_id(true);
++++setcookie('bis_[user_id]',+0,+time()+-+1,+null,+null,+false,+true);
++++setcookie('bis_[session_start]',+0,+time()+-+1,+null,+null,+false,+true);
++++setcookie('bis_[session_time]',+0,+time()+-+1,+null,+null,+false,+true);|code-block|syntax|javascript|790236|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Exceptions are not only used for exceptional circumstances. 

This scenario actually uses exceptions to make sure the user is logged out. At this point in the script it's very resource expensive to figure out what data should be pruned so it's actually faster to just prune it all and catch the exceptions. 

<pre><code> try {
 GDS::$DB-&gt;exec('DELETE FROM sessions WHERE session_id = ' . session_id());
 GDS::$DB-&gt;exec('DELETE FROM sessions WHERE user_id = ' . $this-&gt;data['user_id']);
 } catch(PDOException $ex) {}
 session_regenerate_id(true);
 setcookie('bis_[user_id]', 0, time() - 1, null, null, false, true);
 setcookie('bis_[session_start]', 0, time() - 1, null, null, false, true);
 setcookie('bis_[session_time]', 0, time() - 1, null, null, false, true);
</code></pre>

blocks|key|1744914|text|You+can+with+PHP+8+@see|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1744915|PHP+5,7|1744916|不能，但你可以取消设置。|1744917|try+{
++++...
}+catch+(Exception+$e)+{
++++//+Nothing,+this+is+normal
++++unset($e);
}|code-block|syntax|javascript|1744918|如果是PHPMD导致了这个问题，那么您可以禁止显示该警告。|1744919|PHPMD+suppress-warnings|1744920|class+Bar+{
++++/**
+++++*+This+will+suppress+UnusedLocalVariable
+++++*+warnings+in+this+method
+++++*
+++++*+@SuppressWarnings(PHPMD.UnusedLocalVariable)
+++++*/
++++public+function+foo()+{

++++++++try+{
++++++++++++...
++++++++}+catch+(Exception+$e)+{
++++++++++++//+Nothing,+this+is+normal
++++++++++++unset($e);
++++++++}
++++}
}|1744921|我假设你只是捕获异常，因为你不需要这样做，因为你想这样做。在PHP5，7中，如果你想使用try，你必须使用catch，如果你使用catch，你必须声明一个变量。|style|CODE|1744922|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/61802240/2273611|1|https://phpmd.org/documentation/suppress-warnings.html^0|0|N|0|0|0|0|0|0|0|N|1|0|0|18|3|1H|5|1S|5|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@$A|17|B|18|1|19]]|C|$]]|$1|D|3|E|5|6|7|1A|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|1B|8|@]|9|@]|C|$]]|$1|H|3|I|5|J|7|1C|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|1D|8|@]|9|@]|C|$]]|$1|O|3|P|5|6|7|1E|8|@]|9|@$A|1F|B|1G|1|1H]]|C|$]]|$1|Q|3|R|5|J|7|1I|8|@]|9|@]|C|$K|L]]|$1|S|3|T|5|6|7|1J|8|@$A|1K|B|1L|U|V]|$A|1M|B|1N|U|V]|$A|1O|B|1P|U|V]]|9|@]|C|$]]|$1|W|3|-4|5|6|7|1Q|8|@]|9|@]|C|$]]]|X|$Y|$5|Z|10|11|C|$12|13]]|14|$5|Z|10|11|C|$12|15]]]]

<a href="https://stackoverflow.com/a/61802240/2273611">You can with PHP 8 @see</a> 

PHP 5,7

No, but you can unset it. 

<pre><code>try {
 ...
} catch (Exception $e) {
 // Nothing, this is normal
 unset($e);
}
</code></pre>

If it is PHPMD causing this issue then you can suppress the warning.

<a href="https://phpmd.org/documentation/suppress-warnings.html" rel="nofollow noreferrer">PHPMD suppress-warnings</a> 

<pre><code>class Bar {
 /**
 * This will suppress UnusedLocalVariable
 * warnings in this method
 *
 * @SuppressWarnings(PHPMD.UnusedLocalVariable)
 */
 public function foo() {

 try {
 ...
 } catch (Exception $e) {
 // Nothing, this is normal
 unset($e);
 }
 }
}
</code></pre>

I'm assuming you are only catching the exception because you need to not because you want to. 
With PHP 5,7 you have to use a <code>catch</code> if you want to use <code>try</code> and if you use a <code>catch</code> you have to declare a variable.

blocks|key|4458212|text|我从根本上不同意Marc+B和Artefacto的回答。在某些情况下，省略捕获更好，甚至是唯一的选择。尤其是在使用外部库(您无法控制抛出哪些异常)和/或异步操作时。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4458213|为例：|offset|length|style|BOLD|4458214|我只想创建一个还不存在的文件。我正在使用外部I/O库。假设它有File::exists($fileName)和File::create($fileName)方法。|CODE|4458215|选项1(如果可以省略捕获物)：|4458216|try+{
++++File::create($fileName);
}
//+Go+on+with+the+rest+of+the+code.|code-block|syntax|javascript|4458217|选项2(不带try/catch)：|4458218|if+(!File::exists($fileName))
++++File::create($fileName);|4458219|这里，选项1是完全有效的，因为选项2有两个重要的问题：|4458220|4458221|如果多个线程正在运行并同时通过此代码段，则线程A可能首先检查该文件是否存在。接下来，线程B检查该文件是否存在。他们都发现它并不存在。线程A创建该文件。然后线程B尝试再次创建它，并抛出异常，即使您使用的是if+check.+|ordered-list-item|4458222|，库本身很可能已经执行了!File::exists($fileName)检查。因此，您正在浪费已经进行的调用。|4458223|4458224|请注意，如果File::create抛出了其他可能是意外的异常，最好捕获这些异常。|4458225|结论|4458226|声明某件事从来都不是一个好主意，几乎从来都不是一个好主意。规则总是有例外的(哈哈)。与任何约定或设计模式一样，这只是一条经验法则，旨在帮助经验较少的开发人员做出正确的决策。|4458227|entityMap^0|0|0|3|0|V|N|1J|N|0|0|0|0|0|0|0|0|C|O|0|0|6|C|0|0|2|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1D|8|@$D|1E|E|1F|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|1G|8|@$D|1H|E|1I|F|J]|$D|1J|E|1K|F|J]]|9|@]|A|$]]|$1|K|3|L|5|6|7|1L|8|@]|9|@]|A|$]]|$1|M|3|N|5|O|7|1M|8|@]|9|@]|A|$P|Q]]|$1|R|3|S|5|6|7|1N|8|@]|9|@]|A|$]]|$1|T|3|U|5|O|7|1O|8|@]|9|@]|A|$P|Q]]|$1|V|3|W|5|6|7|1P|8|@]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|10|7|1R|8|@]|9|@]|A|$]]|$1|11|3|12|5|10|7|1S|8|@$D|1T|E|1U|F|J]]|9|@]|A|$]]|$1|13|3|-4|5|6|7|1V|8|@]|9|@]|A|$]]|$1|14|3|15|5|6|7|1W|8|@$D|1X|E|1Y|F|J]]|9|@]|A|$]]|$1|16|3|17|5|6|7|1Z|8|@$D|20|E|21|F|G]]|9|@]|A|$]]|$1|18|3|19|5|6|7|22|8|@]|9|@]|A|$]]|$1|1A|3|-4|5|6|7|23|8|@]|9|@]|A|$]]]|1B|$]]

I disagree fundamentally with Marc B's and Artefacto's answers. There are cases where ommitting the catch is better or even the only option. Especially when using external libraries (where you have no control over what exceptions are thrown) and/or async operations.

For example:

I want to create a file only if it doesn't exist yet. I'm using an external I/O library. Imagine it has <code>File::exists($fileName)</code> and <code>File::create($fileName)</code> methods.

Option 1 (if ommitting the catch was possible):

<pre><code>try {
 File::create($fileName);
}
// Go on with the rest of the code.
</code></pre>

Option 2 (without try/catch):

<pre><code>if (!File::exists($fileName))
 File::create($fileName);
</code></pre>

Here, option 1 is perfectly valid, since option 2 has two important issues:

<ol>
<li>If multiple threads are running and going through this code section at the same time, it could be that thread A first checks if the file exists. Next, thread B checks if the file exists. They both find that it doesn't exist. Thread A creates the file. Thread B then attempts to create it again and throws an exception even though you're using the if check.</li>
<li>It's very likely that the library itself already performs the <code>!File::exists($fileName)</code> check. Therefore you're wasting a call that is already made.</li>
</ol>

Note that if <code>File::create</code> throws other exceptions that might be unexpected it would be good to catch those.

Conclusion

Stating that something is never a good idea, is almost never a good idea. There are always exceptions (hehe) to the rule. Like any convention or design pattern, it's just a rule of thumb meant to help less experienced developers make the right decision.

blocks|key|790390|text|从PHP+8开始，可以使用非捕获catch。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|790391|This+is+the+relevant+RFC，以48比1的赞成票。|offset|length|790392|现在可以这样做了：|790393|try+{
++++readFile($file);
}+catch+(FileDoesNotExist)+{
++++echo+"File+does+not+exist";
}+catch+(UnauthorizedAccess)+{
++++echo+"User+does+not+have+the+appropriate+permissions+to+access+the+file";
++++log("User+attempted+to+access+$file");
}|code-block|syntax|javascript|790394|这样，对于异常细节不相关并且异常类型已经提供了所有必要上下文的一些边缘情况，可以在不创建新变量的情况下捕获异常。|790395|entityMap|0|LINK|mutability|MUTABLE|url|https://wiki.php.net/rfc/non-capturing_catches^0|0|0|O|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@$D|Y|E|Z|1|10]]|A|$]]|$1|F|3|G|5|6|7|11|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|12|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

Starting with PHP 8, it is possible to use a non-capturing catch.
<a href="https://wiki.php.net/rfc/non-capturing_catches" rel="nofollow noreferrer">This is the relevant RFC</a>, which was voted favourably 48-1.
Now it will be possible to do something like this:
<pre><code>try {
 readFile($file);
} catch (FileDoesNotExist) {
 echo &quot;File does not exist&quot;;
} catch (UnauthorizedAccess) {
 echo &quot;User does not have the appropriate permissions to access the file&quot;;
 log(&quot;User attempted to access $file&quot;);
}

</code></pre>
With this, for some edge cases where the exception details are not relevant and exception type already provides all the necessary context, it will be possible to catch the exception without creating a new variable.

blocks|key|1744984|text|从PHP8.0开始，它可以不带变量地输入，但现在每个Exception的大小写都是Throwable。类Exception实现了Throwable。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|CODE|entityRanges|data|1744985|try+{
++++...
}+catch+(CustomException)+{
++++//+CustomException
}+catch+(Throwable)+{
++++//All+other+classes+implementing+Throwable+interface
}|code-block|syntax|javascript|1744986|entityMap^0|1|6|Q|9|15|9|1G|9|1S|9|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|D]|$9|S|A|T|B|D]|$9|U|A|V|B|D]|$9|W|A|X|B|D]]|E|@]|F|$]]|$1|G|3|H|5|I|7|Y|8|@]|E|@]|F|$J|K]]|$1|L|3|-4|5|6|7|Z|8|@]|E|@]|F|$]]]|M|$]]

As of PHP 8.0 it may be typed without variables, but the general case for each <code>Exception</code> is now <code>Throwable</code>. Class <code>Exception</code> implements <code>Throwable</code>.
<pre><code>try {
 ...
} catch (CustomException) {
 // CustomException
} catch (Throwable) {
 //All other classes implementing Throwable interface
}
</code></pre>

blocks|key|790450|text|是的，从PHP8.0开始就可以这样做了。如果你想捕捉所有的异常，你可以使用Throwable。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|CODE|entityRanges|data|790451|try+{
++++...
}+catch+(Exception)+{
++++//+Exception
}+catch+(Throwable)+{
++++//All+other+classes+implementing+Throwable+interface
}|code-block|syntax|javascript|790452|entityMap^0|4|6|11|9|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|D]]|E|@]|F|$]]|$1|G|3|H|5|I|7|S|8|@]|E|@]|F|$J|K]]|$1|L|3|-4|5|6|7|T|8|@]|E|@]|F|$]]]|M|$]]

Yes, you can do it since PHP 8.0. If you want to catch all exceptions you can use <code>Throwable</code>.
<pre><code>try {
 ...
} catch (Exception) {
 // Exception
} catch (Throwable) {
 //All other classes implementing Throwable interface
}
</code></pre>

In PHP, I sometimes catch some exceptions with try/catch :

<pre><code>try {
 ...
} catch (Exception $e) {
 // Nothing, this is normal
}
</code></pre>

With that kind of code, I end up with the variable <code>$e</code> that is created for nothing (lots of resources), and PHP_MD (PHP Mess Detector) creates a warning because of an unused variable.

Is there a way to catch an Exception without having to create a variable?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

在PHP中，我有时会使用try/catch捕获一些异常：try {    ...} catch (Exception $e) {    // Nothing, this is normal}有了这样的代码，我最终得到的是一个无用的变量$e (大量资源)，而PHP_MD (PHP脏乱检测器)会因为一个未使用的变量而创建一...

问有没有一种不需要创建变量就能捕获异常的方法？
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问有没有一种不需要创建变量就能捕获异常的方法？EN