The difference between php exception handling and error handling

The concepts of "error" and "exception" are very similar and can be easily confused. Both "error" and "exception" indicate that there is a problem with the project, and both provide relevant information and error types.

#However, the "exception mechanism" only appeared after the "error mechanism", and "exception" is the shortcoming of avoiding "errors". (Recommended learning: PHP Programming from entry to proficiency)

The more important point is that because the "error" information is not rich, the most common function description we have seen is: Return * when successful **, returns FALSE when an error occurs. However, there may be many reasons for a function error, and there are even more types of errors. A simple FALSE cannot tell the caller the specific error message.

In PHP, exceptions in the code itself (generally caused by illegal environment or syntax) become errors, and logical errors that occur during operation are called exceptions. Errors cannot be handled by the code, and exceptions can be handled by try. /catch processing.

Exception

Exception is an object of the Exception class. It is thrown when encountering an irreparable situation. When a problem occurs, exception is used to take the initiative. By delegating responsibilities, exceptions can also be used defensively to anticipate potential problems and mitigate their impact.

Exception object has two main properties: one is the message and the other is the numeric code. We can obtain these two properties using getCode() and getMessage() respectively.

Exception Handler

So how should we catch every exception that may be thrown? PHP allows us to register a global exception handler to catch all uncaught exceptions. The exception handler is registered using the set_exception_handler() function (anonymous function is used here).

set_exception_handler(function (Exception $e)
{
    echo "我自己定义的异常处理".$e->getMessage();
});
throw new Exception("this is a exception");

//运行结果：我自己定义的异常处理this is a exception

Error

In addition to exceptions, PHP also provides functions for reporting errors. PHP can trigger different types of errors, such as fatal errors, runtime errors, compile-time errors, startup errors, and user-triggered errors. The error reporting method can be set in php.ini (not explained here)

Error handler

Like the exception handler, we also You can use set_error_handler() to register a global error handler and use your own logic to intercept and handle PHP errors. We need to call the die() or exit() function in the error handler. If not called, the PHP script will continue execution from the point where the error occurred. As follows:

set_error_handler(function ($errno,$errstr,$errfile,$errline)//常用的四个参数
{
    echo "错误等级：".$errno."<br>错误信息：".$errstr."<br>错误的文件名：".$errfile."<br>错误的行号：".$errline;
    exit();
});

trigger_error("this is a error");//自行触发的错误

echo &#39;正常&#39;;

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