TalkPHP - exception vs die

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exception vs die

Hi
Well I have never used exceptions, but see some people do, so what is the main difference between those exceptions and die() or echo() and exit() ??

From my viewpoint:
exceptions are the way to go.
Why? Because it's the right way to debug your application if something goes wrong.

Let's use die() for example - it just stops your script. You have to put some code which you want to print out as your debug info.

Exceptions - insystem function that prints the error if any occured on specific part of your code.

Example:

PHP Code:


		
			
<?php

    

    function test( $t ) {

        

        if ( !is_numeric( $t) ) {

            throw new Exception ("You must use only numeric values");

        } else {

            echo $t;

        }

    }

    

    test( '1');

    test( '2');

    test( 'aa' );

?>

Output:

Code:

12

Fatal error: Uncaught exception 'Exception' with message 'You must use only numeric values' in E:\xampplite\htdocs\test\ex.php:6 Stack trace: #0 E:\xampplite\htdocs\test\ex.php(14): test('aa') #1 {main} thrown in E:\xampplite\htdocs\test\ex.php on line 6

The second example:

PHP Code:


		
			
<?php

    

    function test( $t ) {

        

        if ( !is_numeric( $t) ) {

            throw new Exception ("You must use only numeric values");

        } else {

            echo $t;

        }

    }

    

    

    try {

    test( 'a');

}



catch( Exception  $e ) {

        echo $e->getMessage();

}

?>

outputs:
You must use ony numerical values.

So the bottom line:
Error handling is improved.
You can assign your custom error message if there is an error, and you user try{} catch{}.

For me it's the way to go.

Can't wait what the others have to say :-D
Please correct me if I was wrong about something.

So the execution will go directly to

PHP Code:


		
			
catch( Exception  $e ) {

        echo $e->getMessage();

if the exception occurs?

Yes.
Let's say you have a multilingual site.

PHP Code:


		
			
<?php

    

    function test( $t ) {

        global $lang;

        if ( !is_numeric( $t) ) {

            throw new Exception ($lang->NUMERIC_ERROR);

        } else {

            echo $t;

        }

    }

    

    

    try {

    test( 'a');

}



catch( Exception  $e ) {

       // Some error managment

$tmpl->addVar( 'error', $e->getMessage() );

$tmpl->activate( 'errorLayout' );



}

?>

For example.

ok I see :)
Starting to understand it :-)

The exceptions are not a way of ending your script. die and exit are made for that. Exceptions are used to treat various cases and act accordingly. For example:

Code:

function do_division($a, $b)

{

    if( $b == 0 )

   {

        throw new Exception('The divisor cannot be 0!');

   }



    return ($a / $b);

}



try

{

    echo 'Result: ' . do_division(2, 0);

}

catch(Exception $e)

{

    echo $e->getMessage();

    

   // use some default values

   $a = 4;

   $b = 2;

}



// continue execution ...

What about makes using exceptions better than using trigger_error or overwriting that with your own error handler using set_error_handler or calling your own error function?

To me exceptions aren't worth it since you have to use try/catch blocks when I could just use a trigger_error or something similar right where I want the error to be spit out.

I guess if a function or something could return different types of errors then setting up multiple catch blocks would be good. But then again there's ways to do that without using exceptions.

For all questions regarding the advantages and disadvantages of using Exceptions, I refer you to PHP5 Exception Use Guidelines :) Although it is targetted at PEAR developers it is well worth a read, particularly for folks who are new to Exceptions.

Alan