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This article mainly introduces "how to understand PHP object-oriented programming exception handling class Exception". In daily operation, I believe many people have doubts about how to understand PHP object-oriented programming exception handling class Exception. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts of "how to understand PHP object-oriented programming exception handling class Exception"! Next, please follow the editor to study!

Use exception

PHP5 adds exception handling modules similar to those in other languages. Exceptions generated in PHP code can be thrown by throw statements and caught by catch statements. Code that requires exception handling must be placed in a block of try code in order to catch possible exceptions. Each try corresponds to at least one catch block. Using multiple catch, you can catch exceptions generated by different classes. When the try code block no longer throws an exception or the catch can't be found to match the thrown exception, the PHP code continues to execute after jumping to the last catch. Of course, PHP allows (throw) exceptions to be thrown again within the catch code block.

Predefined exception Exception

The Exception class is the base class for all exceptions, and we can customize the exception by deriving the Exception class. The following listing lists the basic information about Exception.

The copy code is as follows:

Exception {

/ * attribute * /

Protected string $message; / / exception message content

Protected int $code; / / exception code

Protected string $file; / / the file name that throws the exception

Protected int $line; / / throw the line number of the exception in the file

/ * method * /

Public _ _ construct ([string $message = "" [, int $code = 0 [, Exception $previous = NULL]) / / exception constructor

Final public string getMessage (void) / / get the content of the exception message

Final public Exception getPrevious (void) / / returns the previous exception in the exception chain

Final public int getCode (void) / / get the exception code

Final public string getFile (void) / / get the name of the program file where the exception occurred

Final public int getLine (void) / / gets the line number of the code that caused the exception in the file

Final public array getTrace (void) / / get exception tracking information

Final public string getTraceAsString (void) / / get exception tracking information of string type

Public string _ _ toString (void) / / convert exception objects to strings

Final private void _ _ clone (void) / / abnormal clone

}

After learning about Exception, let's try to extend the exception class to implement a custom exception.

The copy code is as follows:

Function connectToDatabase ()

{

If (! $link = mysql_connect ("myhost", "myuser", "mypassw", "mybd"))

{

Throw new Exception ("could not connect to the database.")

}

}

Try

{

ConnectToDatabase ()

}

Catch (Exception $e)

{echo $e-> getMessage ()

}

Here we throw an exception of type Exception, catch it in catch, and finally print out "could not connect to the database." You may also want to display information about the reason why the database connection failed. Let's implement our custom information by extending the exception class.

The copy code is as follows:

Class MyException extends Exception

{

Protected $ErrorInfo

/ / deal with some logic in the constructor and then pass some information to the base class

Public function _ _ construct ($message=null,$code=0)

{

$this- > ErrorInfo = 'error message for custom error class'

Parent::__construct ($message,$code)

}

/ / provide a method to obtain custom class information

Public function GetErrorInfo ()

{

Return $this- > ErrorInfo

}

/ * *

*

* you can also add exception logs here, just call it in the constructor above

*

, /

Public function log ($file)

{

File_put_contents ($fiel,$this- > _ _ toString (), FILE_APPEND)

}

}

Function connectToDatabase ()

{

Throw new MyException ("ErrorMessage")

}

Try

{

ConnectToDatabase ()

}

Catch (MyException $e)

{

Echo $e-> getMessage (). "\ n"

Echo $e-> GetErrorInfo ()

}

Set_exception_handler sets a user-defined exception handler

The name of the function called when an uncaught exception occurs as an argument to set_exception_handler. This function must be defined before calling set_exception_handler (). This function takes a parameter, which is an exception object thrown. This can be used to improve the exception logging processing mentioned above.

The copy code is as follows:

Function ExceptionLogger ($exception)

{

$file='ExceptionLog.log'

File_put_contents ($fiel,$exception- > _ _ toString (), FILE_APPEND)

}

Set_exception_handler (ExceptionLogger)

1.3.The PHP allows throw to be thrown again within the catch code block.

The copy code is as follows:

Try

{

# code...

}

Catch (Exception $e)

{

If ($e-> getCode () = = 999)

{

# do some operations

}

Else

{

Throw $e

}

}

At this point, the study on "how to understand the exception handling class Exception of PHP object-oriented programming" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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