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I'm looking for a way to print the call stack in PHP.

Bonus points if the function flushes the IO buffer.

3
  • 2
    possible duplicate of How can I get PHP to produce a backtrace upon errors? Commented Nov 17, 2011 at 9:22
  • 21
    ...but these responses are better. Commented May 7, 2012 at 6:40
  • if it is ordered by quality, then that thread is the duplicated one :D Commented Nov 18, 2022 at 7:19

16 Answers 16

741

More readable than debug_backtrace():

$e = new \Exception; var_dump($e->getTraceAsString()); #2 /usr/share/php/PHPUnit/Framework/TestCase.php(626): SeriesHelperTest->setUp() #3 /usr/share/php/PHPUnit/Framework/TestResult.php(666): PHPUnit_Framework_TestCase->runBare() #4 /usr/share/php/PHPUnit/Framework/TestCase.php(576): PHPUnit_Framework_TestResult->run(Object(SeriesHelperTest)) #5 /usr/share/php/PHPUnit/Framework/TestSuite.php(757): PHPUnit_Framework_TestCase->run(Object(PHPUnit_Framework_TestResult)) #6 /usr/share/php/PHPUnit/Framework/TestSuite.php(733): PHPUnit_Framework_TestSuite->runTest(Object(SeriesHelperTest), Object(PHPUnit_Framework_TestResult)) #7 /usr/share/php/PHPUnit/TextUI/TestRunner.php(305): PHPUnit_Framework_TestSuite->run(Object(PHPUnit_Framework_TestResult), false, Array, Array, false) #8 /usr/share/php/PHPUnit/TextUI/Command.php(188): PHPUnit_TextUI_TestRunner->doRun(Object(PHPUnit_Framework_TestSuite), Array) #9 /usr/share/php/PHPUnit/TextUI/Command.php(129): PHPUnit_TextUI_Command->run(Array, true) #10 /usr/bin/phpunit(53): PHPUnit_TextUI_Command::main() #11 {main}" 
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11 Comments

Damn, this is so much better, why couldn't they make this the default output for debug_print_backtrace()? Could have added a boolean parameter "returnTrace" for those who want it in a variable, not echoed, and it would have been perfect!
I dont know how many months i been trying to figure out how to do that never thought it would work
I was looking for a way to limit debug_backtrace to only return the first level in the stacktrace - this solution does the work for me. Thank you!
@Andrew print_r will retain all the messages.
I dont understand this, where do I put my function or variable I want to backtrace?
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146

If you want to generate a backtrace, you are looking for debug_backtrace and/or debug_print_backtrace.


The first one will, for instance, get you an array like this one (quoting the manual) :

array(2) { [0]=> array(4) { ["file"] => string(10) "/tmp/a.php" ["line"] => int(10) ["function"] => string(6) "a_test" ["args"]=> array(1) { [0] => &string(6) "friend" } } [1]=> array(4) { ["file"] => string(10) "/tmp/b.php" ["line"] => int(2) ["args"] => array(1) { [0] => string(10) "/tmp/a.php" } ["function"] => string(12) "include_once" } } 


They will apparently not flush the I/O buffer, but you can do that yourself, with flush and/or ob_flush.

(see the manual page of the first one to find out why the "and/or" ;-) )

3 Comments

this regularly makes my php run out of memory. I recommend Tobiasz' solution.
If you find it hard to read/understand, I also recommend Tobiasz' solution
@peedee all it takes is to provide one of the optional DEBUG_BACKTRACE_IGNORE_ARGS parameter; that makes them functionally equivalent to (new \Exception())->getTraceAsString()
55

To log the trace

$e = new Exception; error_log(var_export($e->getTraceAsString(), true)); 

Thanks @Tobiasz

Comments

55

Strange that noone posted this way:

debug_print_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS); 

This actually prints backtrace without the garbage - just what method was called and where.

2 Comments

Indeed, really equivalent to the main voted solution, and shorter. Thanks
Where does this print to?
40

Backtrace dumps a whole lot of garbage that you don't need. It takes is very long, difficult to read. All you usuall ever want is "what called what from where?" Here is a simple static function solution. I usually put it in a class called 'debug', which contains all of my debugging utility functions.

class debugUtils { public static function callStack($stacktrace) { print str_repeat("=", 50) ."\n"; $i = 1; foreach($stacktrace as $node) { print "$i. ".basename($node['file']) .":" .$node['function'] ."(" .$node['line'].")\n"; $i++; } } } 

You call it like this:

debugUtils::callStack(debug_backtrace()); 

And it produces output like this:

================================================== 1. DatabaseDriver.php::getSequenceTable(169) 2. ClassMetadataFactory.php::loadMetadataForClass(284) 3. ClassMetadataFactory.php::loadMetadata(177) 4. ClassMetadataFactory.php::getMetadataFor(124) 5. Import.php::getAllMetadata(188) 6. Command.php::execute(187) 7. Application.php::run(194) 8. Application.php::doRun(118) 9. doctrine.php::run(99) 10. doctrine::include(4) ================================================== 

2 Comments

Why not add the parameters to those function calls? Class name is also available for class member functions. You could dd little more code, then out this on GitHub.
11

If you want a stack trace which looks very similar to how php formats the exception stack trace than use this function I wrote:

function debug_backtrace_string() { $stack = ''; $i = 1; $trace = debug_backtrace(); unset($trace[0]); //Remove call to this function from stack trace foreach($trace as $node) { $stack .= "#$i ".$node['file'] ."(" .$node['line']."): "; if(isset($node['class'])) { $stack .= $node['class'] . "->"; } $stack .= $node['function'] . "()" . PHP_EOL; $i++; } return $stack; } 

This will return a stack trace formatted like this:

#1 C:\Inetpub\sitename.com\modules\sponsors\class.php(306): filePathCombine() #2 C:\Inetpub\sitename.com\modules\sponsors\class.php(294): Process->_deleteImageFile() #3 C:\Inetpub\sitename.com\VPanel\modules\sponsors\class.php(70): Process->_deleteImage() #4 C:\Inetpub\sitename.com\modules\sponsors\process.php(24): Process->_delete() 

2 Comments

or just $e = new Exception; echo $e->getTraceAsString();
Brad, that solution doesn't remove the last item from the stack trace so you don't show the trace item caused by the new Exception
8
var_dump(debug_backtrace()); 

Does that do what you want?

Comments

7

If one is just interested in the files called - you can use the following:

print_r(array_column(debug_backtrace(),'file'));

Likewise you can replace file with a different key just to see that data.

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6

See debug_print_backtrace. I guess you can call flush afterwards if you want.

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6

phptrace is a great tool to print PHP stack anytime when you want without installing any extensions.

There are two major function of phptrace: first, print call stack of PHP which need not install anything, second, trace php execution flows which needs to install the extension it supplies.

as follows:

$ ./phptrace -p 3130 -s # phptrace -p <PID> -s phptrace 0.2.0 release candidate, published by infra webcore team process id = 3130 script_filename = /home/xxx/opt/nginx/webapp/block.php [0x7f27b9a99dc8] sleep /home/xxx/opt/nginx/webapp/block.php:6 [0x7f27b9a99d08] say /home/xxx/opt/nginx/webapp/block.php:3 [0x7f27b9a99c50] run /home/xxx/opt/nginx/webapp/block.php:10 

2 Comments

Is there a Windows version?
I like the memory address are shown here.. This can be helpful
6

Walltearer's solution is excellent, particularly if enclosed in a 'pre' tag:

<pre> <?php debug_print_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS); ?> </pre> 

- which sets out the calls on separate lines, neatly numbered

Comments

3

Use debug_backtrace to get a backtrace of what functions and methods had been called and what files had been included that led to the point where debug_backtrace has been called.

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2

please take a look at this utils class, may be helpful:

Usage:

<?php /* first caller */ Who::callme(); /* list the entire list of calls */ Who::followme(); 

Source class: https://github.com/augustowebd/utils/blob/master/Who.php

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2

I have adapted Don Briggs's answer above to use internal error logging instead of public printing, which may be your big concern when working on a live server. Also, added few more modifications like option to include full file path instead of basic name (because, there could be files with same name in different paths), and also (for those who require it) a complete node stack output:

class debugUtils { public static function callStack($stacktrace) { error_log(str_repeat("=", 100)); $i = 1; foreach($stacktrace as $node) { // uncomment next line to debug entire node stack // error_log(print_r($node, true)); error_log( $i . '.' . ' file: ' .$node['file'] . ' | ' . 'function: ' . $node['function'] . '(' . ' line: ' . $node['line'] . ')' ); $i++; } error_log(str_repeat("=", 100)); } } // call debug stack debugUtils::callStack(debug_backtrace()); 

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1

debug_backtrace()

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1

You might want to look into debug_backtrace, or perhaps debug_print_backtrace.

Comments

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