Xdebug
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This document summarizes Tobias Schlitt's presentation on the Xdebug debugger for PHP. It discusses how Xdebug can enhance PHP development by providing more useful error messages, improved variable dumping, and protection from infinite loops. It also describes Xdebug's features for retrieving stack traces and declared variables. A key part of Xdebug is its ability to trace PHP applications and analyze the control flow, which can help debug issues without needing to add trace statements throughout code.
![Useful functions
xdebug [en/dis ] able ()
Manually switch stack traces on or off
xdebug call [ class /function/ file / line ]()
Get the call point of the currently running function
xdebug dump superglobals()
Dump super-globals as specified by INI setting
Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 22 / 41](https://image.slidesharecdn.com/xdebugpresentation-091125051956-phpapp02/85/Xdebug-31-320.jpg)
Xdebug
- 1. Xdebug Alltagshilfe und professioneller Debugger TobiasSchlitt <toby@php.net> PHP World Kongress 2009 2009-11-24 Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 1 / 41
- 2. About me Tobias Schlitt <toby@php.net> PHP since 2001 Freelancing consultant Qualified IT Specialist Studying CS at TU Dortmund (finishing mid 2010) OSS addicted eZ Components PHPUnit Various other projects . . . Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 2 / 41
- 3. Overview 1 About Debugging 2 Installation 3 Development goodies 4 Tracing 5 More features... 6 The end Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 3 / 41
- 4. Outline 1 About Debugging 2 Installation 3 Development goodies 4 Tracing 5 More features... 6 The end Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 4 / 41
- 5. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 6. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 7. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 8. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 9. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 10. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 11. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 12. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 13. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 14. Why a debugger? I don’t need a debugger No bug free code Living life the easy way . . . var dump(), print r() and echo Sometimes, yes Slow and a lot of work Using a debugger = using an IDE No, but you can Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 5 / 41
- 15. What is Xdebug? Open Source debugger for PHP PHP (Zend Engine) extension Works (at least) on Linux, Mac and Windows About 5 years old Current stable version: 2.0.5 Created and maintained by Derick Rethans http://xdebug.org Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 6 / 41
- 16. Xdebug features Enhance daily work with PHP Trace PHP program runs Profile PHP applications Analyze code coverage (e.g. PHPUnit) Remote-debugging with an external client Including break-points, stepping, . . . Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 7 / 41
- 17. Outline 1 About Debugging 2 Installation Installation Configuration 3 Development goodies 4 Tracing 5 More features... 6 The end Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 8 / 41
- 18. Via PEAR Easiest way to install Working PEAR assumed: $ pear install pecl/xdebug PEAR Installer performs necessary steps: 1 Download source 2 Compiling module 3 Copying module to destination After that: Add module to php.ini Only on *nix systems Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 9 / 41
- 19. Manual Compile by hand Typical PHP module compile process wget h t t p : / / xdebug . o r g / l i n k . php ? u r l=xdebug205 t a r −x z f xdebug − 2 . 0 . 5 . t g z cd xdebug − 2 . 0 . 5 phpize . / c o n f i g u r e −−enable −xdebug −−w i t h −php−c o n f i g =/ u s r / b i n / php−c o n f i g make cp m o d u l e s / xdebug . s o /<m o d u l e p a t h >/xdebug . s o After that: Add module to php.ini Only on *nix systems Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 10 / 41
- 20. Windows Download binary module from http://xdebug.org Copy to modules directory After that: Add module to php.ini Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 11 / 41
- 21. Add module to php.ini Not a “normal” extension Add to php.ini: zend extension = ”/path/to/xdebug.so” For threadsafe builds: zend extension ts For debug builds zend extension debug Check $ php −v or phpinfo() ; Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 12 / 41
- 22. Common pitfalls extension dir directive does not take effect! Binary modules (Windows) do not work with PHP debug builds −−enable−versioning prevents loading Other zend-extensions interfere with Xdebug Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 13 / 41
- 23. Configuration Huge variety of options Many shown later Overview: http://xdebug.org/docs/all_settings Most options adjustably with ini set () at runtime, except for xdebug.extended info xdebug. profiler ∗ Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 14 / 41
- 24. Outline 1 About Debugging 2 Installation 3 Development goodies Error messages Dumping variables Infinity Useful functions 4 Tracing 5 More features... 6 The end Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 15 / 41
- 25. Getting started Install module Switch it on Tweak some settings Work as usual Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 16 / 41
- 26. Error messages PHP error messages not very useful Sometimes poor error location Almost no info on affected data No info on code context Xdebug enhances that for you! Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 17 / 41
- 27. Let’s dig into some code Let’s dig into some code Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 18 / 41
- 28. var dump() Using var dump() Everyone does it There is nothing bad about it var dump() in the browser sucks Xdebug enhances var dump() Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 19 / 41
- 29. Infinite loops Endless recursions Extremely hard to find Script just times out . . . or worse! Xdebug can protect you Note: Not from endless runs of loops! Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 20 / 41
- 30. Let’s dig into some code Let’s dig into some code Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 21 / 41
- 31. Useful functions xdebug [en/dis ] able () Manually switch stack traces on or off xdebug call [ class /function/ file / line ]() Get the call point of the currently running function xdebug dump superglobals() Dump super-globals as specified by INI setting Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 22 / 41
- 32. Useful functions xdebug get declared vars () Returns an array containing the names of all variables in the current scope xdebug get function stack () Returns the function stack trace as an array xdebug get stack depth() Get the current depth in the function stack Note: Includes also create a level! Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 22 / 41
- 33. Let’s dig into some code Let’s dig into some code Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 23 / 41
- 34. Declared vars Getting declared variables f u n c t i o n f o o ( $a , $b ) { g l o b a l $c ; $d = ’ I am l o c a l ’ ; var dump ( x d e b u g g e t d e c l a r e d v a r s ( ) ) ; } $c = ’ I am g l o b a l ’ ; f o o ( 2 3 , 42 ) ; Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 24 / 41
- 35. Let’s dig into some code Let’s dig into some code Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 25 / 41
- 36. Stack depth Retrieving stack level echo ”<p r e >” ; echo ” S t a c k d e p t h i n ” . FILE . ”: ” . x d e b u g g e t s t a c k d e p t h ( ) . ” nn” ; function foo () { echo ” S t a c k d e p t h i n ” . FUNCTION . ”: ” . x d e b u g g e t s t a c k d e p t h ( ) . ” nn” ; bar () ; } i n c l u d e ’ s t a c k d e p t h / d e e p e r s t a c k . php ’ ; Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 26 / 41
- 37. Let’s dig into some code Let’s dig into some code Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 27 / 41
- 38. Outline 1 About Debugging 2 Installation 3 Development goodies 4 Tracing 5 More features... 6 The end Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 28 / 41
- 39. What is tracing? Check control flow of application Correct function calls Correct data Does input data produce correct workflow? Traces always depend on input data Almost impossible to create traces for every possible control flow Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 29 / 41
- 40. Tracing Some developers trace like this: echo ” Here I am ! ! ! ” ; // . . . echo ”Now I ’m h e r e ! ! ! Something i s : ” ; var dump ( $ s o m e t h i n g ) ; Works well in small scripts Horror in larger apps / libraries Debugging like this is a sh**load of work Almost impossible with 3rd party code Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 30 / 41
- 41. Tracing with Xdebug By functions: xdebug start trace () xdebug stop trace () Automatically (php.ini) xdebug.auto trace = ”1” Cannot be set via ini set () ! Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 31 / 41
- 42. Tracing example A simple trace f u n c t i o n d o u b l e F a c u l t y ( $num ) { i f ( $num < 3 ) { r e t u r n $num ; } r e t u r n $num ∗ d o u b l e F a c u l t y ( $num − 2 ) ; } x d e b u g s t a r t t r a c e ( ’ t r a c e s /60 s i m p l e t r a c e . x t ’ ) ; echo d o u b l e F a c u l t y ( 10 ) ; Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 32 / 41
- 43. Let’s dig into some code Let’s dig into some code Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 33 / 41
- 44. Notes on tracing Never trace in production! Tracing is extremely slow! grep & friends help a lot Tuning configuration makes traces more usable More information through Xdebug mean Slower performance Higher memory consumption Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 34 / 41
- 45. Outline 1 About Debugging 2 Installation 3 Development goodies 4 Tracing 5 More features... 6 The end Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 35 / 41
- 46. Profiling Which code takes which time? Find bottle necks in code Check your database queries and setup first! Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 36 / 41
- 47. Code coverage Mostly used in testing Which code is not covered by a test? PHPUnit can utilize this http://www.phpunit.de Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 37 / 41
- 48. Remote debugging Integrate Xdebug into your IDE Komodo IDE Eclipse Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 38 / 41
- 49. Outline 1 About Debugging 2 Installation 3 Development goodies 4 Tracing 5 More features... 6 The end Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 39 / 41
- 50. Questions / Answers Questions? Feedback? Critics? Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 40 / 41
- 51. The end I hope you enjoyed the session Slides and material http://schlitt.info/opensource http://www.slideshare.net/tobyS Contact: Tobias Schlitt <toby@php.net> Tobias Schlitt (PHP World Kongress 2009) Xdebug 2009-11-24 41 / 41