PHP try-catch block inside loop

Question

Is it less efficient to put a try-catch block inside of a loop as opposed to wrapping the loop with a try-catch in php if it is intended that the loop will end if an exception occurs? Or is there essentially no difference?

EDIT:

i.e.,

foreach (/*...*/) {
    //...
    try {
        //...
    } catch (/*...*/) {
        break;
    }
    //...
}

versus:

try {
    foreach (/*...*/) {
        //...
    }
}

it may be surprised you, but sometimes code being written to be sensible, not to be "more efficient" nonsense. Just sensible. To make a task it's designated for. — Your Common Sense, Jan 12 '11 at 20:26
Could the performance penalty of having a try-catch block inside a loop as opposed to being outside be approximately the same as the penalty for `for ($i = 0; $i < count($array); $i++) {...}` as opposed to `for ($i = 0; $i < $arrayCount; $i++) {...}` — Uyghur Lives Matter, Jan 12 '11 at 20:48

Peter Bailey · Answer 1 · 2016-04-13T18:22:57.510

64

That entirely depends on the nature of the failure, and what you intend to do in the catch.

But I'd generalize it like so

If you want the loop to exit on Exception, wrap the whole loop
If you want the loop to continue, don't

EDIT

Exceptions caught inside a loop don't implicitly break the loop

for ($i = 1; $i < 10; $i++) {
    try {
        if ($i % 3 == 0) {
            throw new Exception('BOOM');
        }
        echo $i;
    } catch (Exception $e) {
        echo "Exception at $i";
    }
    echo PHP_EOL;
}

output:

1
2
Exception at 3
4
5
Exception at 6
7
8
Exception at 9

Whereas those caught outside the loop do

try {
    for ($i = 1; $i < 10; $i++) {
        if ($i % 3 == 0) {
            throw new Exception('BOOM');
        }
        echo $i, PHP_EOL;
    }
} catch ( Exception $e ) {
    echo "Exception at $i";
}

output:

1
2
Exception at 3

edited Apr 13 '16 at 18:22

answered Jan 12 '11 at 20:10

Peter Bailey

105,256
31
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1

The loop will break if an exception occurs. – Uyghur Lives Matter Jan 12 '11 at 20:13
2

Not if the exception is caught. I'll add an example – Peter Bailey Jan 12 '11 at 20:34
I mean the loop is intended to break if an exception is caught: `foreach (...) { try {...} catch(...) { break; } }` – Uyghur Lives Matter Jan 12 '11 at 20:37
1

if you want to break loop on exception , put `try .. catch` outside of the loop. – German Rumm Jan 12 '11 at 21:03
2

good example, thanks! – Emiliano Oct 28 '16 at 15:19
If the exception is caught and not thrown again they yes, it will depend on how much the try/catch covers and if it is outside it will break the whole loop, but if u throw it again it will stop the loop also if it is inside, there could be many reasons u would still want to do that like being sure nothing is processed further than this line, but u are only concerned about that line. – Programista Jul 28 '22 at 20:43

score 2 · Answer 2 · answered Jan 12 '11 at 20:09

2

That depends entirely on how you are using the try-catch? Is it safe to continue looping through your subject if an exception was thrown?

answered Jan 12 '11 at 20:09

Craige

2,882
2
20
28

score 1 · Answer 3 · answered Jan 12 '11 at 20:09

There is most likely no difference. Optimization on this level does usually not make any sense in an interpreted language like PHP.

In most cases, your logic will require you to put the block inside the loop anyway. Otherwise, the loop will continue even if an error has occurred.

score 0 · Answer 4 · answered Jan 12 '11 at 20:11

Of course, there's a difference, in the most obvious way int the first case you will only check for errors before entering the loop, if the loop doesn't have exception throwers, leave it that way. In the other hand you will be checking it in each iteration, wich you'll need if you have sentences or methods ... wich can have exceptions.

I'dont know if i explain myself well, let me know if you understand

PHP try-catch block inside loop

4 Answers4

EDIT

Linked