为什么 PHP 没有捕获“找不到类”错误？
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Why doesn't PHP catch a "Class not found" error?
提问by Edward Tanguay
In the following example, if the class does not exist, I want to catch the error and create a Nullclass instead.
在以下示例中，如果该类不存在，我想捕获错误并创建一个Null类。
But in spite of my try/catch statements, PHP simply tells me Class 'SmartFormasdfasdf' not found.
但是尽管我有 try/catch 语句，PHP 只是告诉我Class 'SmartFormasdfasdf' not found.
How can I get PHP to catch the 'class not found' error?
如何让 PHP 捕获“找不到类”错误？
<?php
class SmartFormLogin extends SmartForm {
public function render() {
echo '<p>this is the login form</p>';
}
}
class SmartFormCodeWrapper extends SmartForm {
public function render() {
echo '<p>this is the code wrapper form</p>';
}
}
class SmartFormNull extends SmartForm {
public function render() {
echo '<p>the form "' . htmlentities($this->idCode) . '" does not exist</p>';
}
}
class SmartForm {
protected $idCode;
public function __construct($idCode) {
$this->idCode = $idCode;
}
public static function create($smartFormIdCode) {
$className = 'SmartForm' . $smartFormIdCode;
try {
return new $className($smartFormIdCode);
} catch (Exception $ex) {
return new SmartFormNull($smartformIdCode);
}
}
}
$formLogin = SmartForm::create('Login');
$formLogin->render();
$formLogin = SmartForm::create('CodeWrapper');
$formLogin->render();
$formLogin = SmartForm::create('asdfasdf');
$formLogin->render();
?>
Solution:
解决方案：
Thanks @Mchl, this is how I solved it then:
谢谢@Mchl，这就是我解决它的方法：
public static function create($smartFormIdCode) {
$className = 'SmartForm' . $smartFormIdCode;
if(class_exists($className)) {
return new $className($smartFormIdCode);
} else {
return new SmartFormNull($smartFormIdCode);
}
}
回答by Mchl
Because it's a fatal error. Use class_exists() function to check if class exist.
因为这是一个致命的错误。使用 class_exists() 函数检查类是否存在。
Also: PHP is not Java - unless you redefined default error handler, it will raise errors and not throw exceptions.
另外：PHP 不是 Java - 除非您重新定义默认错误处理程序，否则它将引发错误而不是抛出异常。
回答by ChadSikorra
Old question, but in PHP7 this is a catchable exception. Though I still think the class_exists($class)is a more explicit way to do it. However, you could do a try/catch block using the new \Throwableexception type:
老问题，但在 PHP7 中，这是一个可捕获的异常。尽管我仍然认为这class_exists($class)是一种更明确的方法。但是，您可以使用新的\Throwable异常类型执行 try/catch 块：
$className = 'SmartForm' . $smartFormIdCode;
try {
return new $className($smartFormIdCode);
} catch (\Throwable $ex) {
return new SmartFormNull($smartformIdCode);
}
回答by Horace
php >= 7.0
php >= 7.0
php can catch 'class not found' as Throwable
php 可以将“找不到类”捕获为 Throwable
try {
return new $className($smartFormIdCode);
} catch (\Throwable $ex) {
return new SmartFormNull($smartformIdCode);
}
回答by John Parker
You need to use class_existsto see if the class exists before you try and instantiate it.
在尝试实例化它之前，您需要使用class_exists来查看该类是否存在。
Incidentally, if you're using a class autoloader, be sure to set the second arg to true.
顺便说一句，如果您使用的是类自动加载器，请务必将第二个参数设置为 true。
回答by dev-null-dweller
Because php emits fatal error when you ty to create new object of non existing class. To make it work you will need php >= 5.3 and autoloadfunction, where you should try to look for file with class definition or throw your custom exception.
因为当您创建非现有类的新对象时，php 会发出致命错误。要使其工作，您将需要 php >= 5.3 和自动加载功能，您应该尝试在其中查找具有类定义的文件或抛出您的自定义异常。
