What's the `finally` keyword for in PHP?

Question

Consider these two examples

<?php
function throw_exception() {
    // Arbitrary code here
    throw new Exception('Hello, Joe!');
}

function some_code() {
    // Arbitrary code here
}

try {
    throw_exception();
} catch (Exception $e) {
    echo $e->getMessage();
}

some_code();

// More arbitrary code
?>

and

<?php
function throw_exception() {
    // Arbitrary code here
    throw new Exception('Hello, Joe!');
}

function some_code() {
    // Arbitrary code here
}

try {
    throw_exception();
} catch (Exception $e) {
    echo $e->getMessage();
} finally {
    some_code();
}

// More arbitrary code
?>

What's the difference? Is there a situation where the first example wouldn't execute some_code(), but the second would? Am I missing the point entirely?

`Code within the finally block will always be executed after the try and catch blocks, regardless of whether an exception has been thrown, and before normal execution resumes.` — Dave Chen, Jun 25 '13 at 08:52
I think this is related on this thread: http://stackoverflow.com/questions/15031515/can-i-use-try-catch-finally-like-this — JunM, Jun 25 '13 at 08:53
Just to save anyone else copy-pasting from the PHP manual, I have read that but don't understand the difference between these two examples, otherwise I wouldn't have asked the question. — marxjohnson, Jun 25 '13 at 08:56

score 43 · Accepted Answer · edited Jun 25 '13 at 09:02

43

If you catch Exception (any exception) the two code samples are equivalent. But if you only handle some specific exception type in your class block and another kind of exception occurs, then some_code(); will only be executed if you have a finally block.

try {
    throw_exception();
} catch (ExceptionTypeA $e) {
    echo $e->getMessage();
}

some_code(); // Will not execute if throw_exception throws an ExceptionTypeB

but:

try {
    throw_exception();
} catch (ExceptionTypeA $e) {
    echo $e->getMessage();
} finally {
    some_code(); // Will be execute even if throw_exception throws an ExceptionTypeB
}

edited Jun 25 '13 at 09:02

Mark Baker

209,507
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answered Jun 25 '13 at 08:58

Simon

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1

Worth a +1 for citing a specific instance when `some_code()` will not be executed – Mark Baker Jun 25 '13 at 09:02
I have spent a while researching why they are at all useful, and finally (no pun intended), your answer gives a valid reasoning for the necessity of a finally block. – Jeffrey Cordero Jul 21 '16 at 20:15

score 0 · Answer 2 · answered Jun 25 '13 at 08:56

0

fianlly block is used when you want a piece of code to execute regardless of whether an exception occurred or not...

Check out Example 2 on this page :

PHP manual

answered Jun 25 '13 at 08:56

Ashrith Sheshan

654
4
17

score 0 · Answer 3 · answered Jan 12 '18 at 05:12

Finally will trigger even if no exception were caught.

Try this code to see why:

<?php
class Exep1 extends Exception {}
class Exep2 extends Exception {}

try {
  echo 'try ';
  throw new Exep1();
} catch ( Exep2 $e)
{
  echo ' catch ';
} finally {
  echo ' finally ';
}

echo 'aftermath';

?>

the output will be

try  finally 
Fatal error: Uncaught exception 'Exep1' in /tmp/execpad-70360fffa35e/source-70360fffa35e:7
Stack trace:
#0 {main}
  thrown in /tmp/execpad-70360fffa35e/source-70360fffa35e on line 7

here is fiddle for you. https://eval.in/933947

score 0 · Answer 4 · answered Sep 17 '18 at 14:03

From the PHP manual:

In PHP 5.5 and later, a finally block may also be specified after or instead of catch blocks. Code within the finally block will always be executed after the try and catch blocks, regardless of whether an exception has been thrown, and before normal execution resumes.

See this example in the manual, to see how it works.

score -2 · Answer 5 · answered Jun 25 '13 at 08:53

-2

http://www.youtube.com/watch?v=EWj60p8esD0

Watch from: 12:30 onwards

Watch this video. The language is JAVA though. But i think it illustrates Exceptions and the use of finally keyword very well.

answered Jun 25 '13 at 08:53

sodhancha

435
15
31

Thanks soden, that explains what I already know, i.e. that it runs regardless of whether there's an exception. But so does code placed after the block, doesn't it? Is there a specific advantage to having it as part of the block? – marxjohnson Jun 25 '13 at 08:59
Depends on how much you want the exception to be abstracted from the user. Generally speaking using finally is a rarity. – sodhancha Jun 25 '13 at 09:04

What's the `finally` keyword for in PHP?

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