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?

Monomial

Answer 1

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());

Pacifistic

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. – Shew

@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." – Bloat

Answer 2

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

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

Eparch

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. – Keepsake

Or as a one-liner: (new \Exception())->getTraceAsString() – Impresario

And in PHP 7+, slightly shorter: (new \Error)->getTraceAsString() – Thorvaldsen

Answer 3

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

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

Homocercal

var_export does not handle circular references. Therefore that solution is not safe to use. – Keepsake

Answer 4

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

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

Batey

Answer 5

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()));

Transitory

Answer 6

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()));

Epigeous