How can I save a PHP backtrace to the error log?

Question

I'm using this right now:

error_log(serialize(debug_backtrace()));

But I have to unserialize it every time. Is there a better way to store backtraces?

Álvaro González · Accepted Answer · 2017-07-13T14:31:23.673

65

This should generate a readable string:

error_log(print_r(debug_backtrace(), true));

Additionally, debug_print_backtrace() prints the back trace as string and its output can be captured with regular output buffer functions:

ob_start();
debug_print_backtrace();
error_log(ob_get_clean());

edited Jul 13 '17 at 14:31

answered Dec 03 '11 at 17:04

Álvaro González

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`debug_backtrace()` returns a big array, which doesn't print_r real well. The second method prints a nicer looking backtrace. Another method I sometimes use is just `error_log(new Exception('message here, if you want'));` because I like the way the backtrace is formatted for exceptions. – Jay K Oct 14 '16 at 20:24
1

@JayK - FWIW, sassman on a comment on Igor's answer says about Exception: *"But it does not include the variables of the calling scope. The benefit of debug_print_backtrace() is it includes a copy of the runtime context."* – ToolmakerSteve Apr 17 '19 at 19:15

score 24 · Answer 2 · answered Nov 09 '16 at 13:16

24

From my perspective the best approach is using an exception functionality:

$e = new Exception();
$e->getTraceAsString();

answered Nov 09 '16 at 13:16

Igor Sydorenko

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it prints the trace, yes. But it does not include the variables of the calling scope. The benefit of debug_print_backtrace() is it includes a copy of the runtime context. – 5422m4n Sep 14 '17 at 11:39
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Or as a one-liner: `(new \Exception())->getTraceAsString()` – Giel Berkers Jan 25 '18 at 09:00
And in PHP 7+, slightly shorter: `(new \Error)->getTraceAsString()` – bishop Oct 24 '18 at 20:11

score 8 · Answer 3 · edited Jun 11 '13 at 12:46

8

    $log = var_export(debug_backtrace(), true);

Then use the variable $log to log in file or what ever.

edited Jun 11 '13 at 12:46

Mathias Lykkegaard Lorenzen

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answered Jun 07 '12 at 04:07

Pramendra Gupta

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var_export does not handle circular references. Therefore that solution is not safe to use. – 5422m4n Sep 14 '17 at 11:34

score 4 · Answer 4 · edited Jun 11 '13 at 12:46

4

A little ugly but workable, I do this:

 error_log('Identifying string so that it doesn\'t just end up as gibberish' . json_encode(debug_backtrace()));

edited Jun 11 '13 at 12:46

Mathias Lykkegaard Lorenzen

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answered Dec 03 '11 at 17:01

Kzqai

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score 3 · Answer 5 · answered Jul 18 '20 at 14:47

3

For those who might want a more compact version, this will also do the trick:

error_log((new Exception())->getTraceAsString())

answered Jul 18 '20 at 14:47

Nicolas Bouvrette

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score 1 · Answer 6 · answered Apr 17 '19 at 05:53

1

The following can either be written to a .txt file or you can also access it's contents (like $content[0]) as opposed to var_export which is a bit trickier I find:

    $content = unserialize(serialize(debug_backtrace()));

answered Apr 17 '19 at 05:53

Robert Sinclair

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How can I save a PHP backtrace to the error log?

6 Answers6

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