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Debugging Effectively - php[world] 2015

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Colin O'Dell

The document outlines the critical importance of debugging in programming, emphasizing it as a fundamental skill for developers. It presents a systematic approach to debugging, including gathering information, replicating issues, identifying culprits, and fixing them while suggesting various tools and techniques to enhance the debugging process. The document also encourages developers to learn from their debugging experiences to improve their skills and methodologies over time.

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Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Debugging Effectively Colin O’Dell
Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Colin O’Dell • Lead Web Developer at Unleashed Technologies • PHP developer since 2002 • Certifications: Symfony and Magento • PHP League Member • league/commonmark • league/html-to-markdown • PHP 7 Upgrade Guide e-book • @colinodell / www.colinodell.com
Overview I. Importance of debugging II. Debugging process III. Tools & Techniques IV. Q&A Photo by Roman Boed // cc by 2.0 // https://flic.kr/p/ngwcf1
Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (adjective)
Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m important
Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m the single most important skill in programming.
Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC PlanningCoding
Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC Planning Testing & Debugging Coding
Debugging is the process of finding and resolving bugs or defects that prevent correct operation of computer software or a system. – Wikipedia Photo by Stephen Dyrgas // cc by-nc-nd 2.0 // https://flic.kr/p/3eTfWU
Process is the foundation of effective debugging Process Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa
Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa Gain experience with tools and code Experience Process
Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa Develop a “sixth sense” “Sixth Sense” Experience Process
Junior Developers • Try the “usual” steps • Clear the cache • Re-install dependencies • chmod –R 777 * • Google the error • Try every solution • Ask somebody else • Co-worker • StackOverflow post • Give up Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL
XY Problem Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL •I want to solve problem X •How do I solve X?
XY Problem Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL •I want to solve problem X •How do I solve X? •Solution Y might work •How can I do Y?
Photo by quattrostagioni // cc by 2.0 // https://flic.kr/p/aGjVq8 1.Don’t parse HTML with regex 2.Solve problems the right way
“I don’t know why” “For some reason” “Doesn’t make sense” Photo by Stanley Yuu // cc by-nc-nd 2.0 // https://flic.kr/p/pMnfNu
Bugs are logical Photo by Photofest
“The bug is not moving around in your code, trying to trick or evade you. It is just siting in one place, doing the wrong thing in the same way every time.” – Nick Parlante, Debugging Zen Photo by GrahamC57 // cc by-nc-nd 2.0 // https://flic.kr/p/cwJi9Q
Assume your code is the problem Photo by Sergio Flores Rosales // cc by-nc-nd 2.0 // https://flic.kr/p/5UHkaW
Systematic Approach 1. Gather information 2. Replicate the issue 3. Identify the culprit 4. Fix it & re-test 5. Mitigate future occurrences Photo from EduSpiral // cc by-nc-nd 3.0
1. Gather information • Expected behavior vs. actual behavior • Error messages • Stack traces Photo from youmustdesireit.wordpress.com •Screenshots •Browser & OS •Date & time •Log entries
2. Replicate the Issue Be able to replicate with 100% certainty Photo by Nick Royer // cc by-sa // https://flic.kr/p/d41ASC
3. Identify the Culprit Photo by U.S. Navy // cc 2.0 // https://flic.kr/p/n6Wgks • Be methodical • Make no assumptions • Understand the bug
4. Fix it & Re-test • Attempt to replicate again • Avoid XY problem • No temporary workarounds! • Add technical debt • May introduce other issues • Never get replaced with true solutions Photo by Jeff Eaton // cc by-sa 2.0 // https://flic.kr/p/b33rSx
5. Mitigate Future Occurrences • Add an automated test • Share your new knowledge • Project documentation • Blog post • StackOverflow • Submit patch upstream Photo by marcokalmann // cc by-nc-nd 2.0 // https://flic.kr/p/4CqLMQ
Recap 1. Gather information 2. Replicate the issue 3. Identify the culprit 4. Fix it & re-test 5. Mitigate future occurrences Photo from EduSpiral // cc by-nc-nd 3.0
Long-Term Results • Gain experience • Learn how the system works • Build heuristics • Boost confidence Photo by Glenn Beltz // cc by 2.0 // https://flic.kr/p/i7Csdx
Tools & Techniques Photo by Alan // cc by-nc-sa 2.0 // https://flic.kr/p/9azLii
Two essential tools • Integrated development environment (IDE) • Interactive debugger Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
Integrated Development Environment •Minimum features: •Syntax highlighting •Auto-completion •Fast code navigation •Debugger Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
Interactive Debugger •Pause code execution •Breakpoints •Conditional breakpoints •Step through execution •Examine variables •Explore call stack Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
Debugging Effectively - php[world] 2015
Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
Techniques 1. Trace backwards from known issue 2. Divide & conquer 3. Use tools 4. Get help 5. Take a break Photo by Massmo Relsig // cc by-nc-nd 2.0 // https://flic.kr/p/pFrJCe
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
2. Divide & Conquer • Identify different code sections • Set breakpoints at the boundaries • Isolate issue to one particular area • Focus efforts on that area
Debugging Effectively - php[world] 2015
Debugging Effectively - php[world] 2015
Debugging Effectively - php[world] 2015
✓ X
Debugging Effectively - php[world] 2015
3. Use tools • Automated tests • Kint / VarDumper • Debug toolbars • Console utility • Profilers • git bisect •netcat •curl •etc. Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
Automated Tests Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe
Kint Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Kint::dump($var);
VarDumper Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Twig: {{ dump(foo) }} {% dump foo %} PHP: dump($somevar);
Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Debug toolbars
Console Utility Symfony: app/console Drupal: drush Magento: n98-magerun.phar Laravel: artisan Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe
Performance Profiling Identify slowness: • Bottlenecks • Resource hogs • Inefficient code Photo by Alan Stark // cc by-sa 2.0 // https://flic.kr/p/dn3qjx Tools: • Blackfire (freemium) • New Relic (freemium) • xhprof (open-source)
Blackfire Photo by Alan Stark // cc by-sa 2.0 // https://flic.kr/p/dn3qjx
New Relic Photo by Alan Stark // cc by-sa 2.0 // https://flic.kr/p/dn3qjx
git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect start git bisect bad
git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect good
git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect bad
git bisect v1.7 ? ? ? BAD ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect bad
git bisect v1.7 ? ? ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect good
git bisect v1.7 ? GOOD ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect good
git bisect v1.7 GOOD GOOD ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm
git bisect v1.7 GOOD GOOD X BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm abcd123 is the first bad commit
Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe netcat
Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe curl
4. Get help • RTFM / RTFD • Project forums or issue queue • StackOverflow, IRC, etc. • Ask a colleague • Expert in that area • Senior developer • Rubber ducking Photo by Hiromitsu Morimoto // cc by-sa 2.0 // https://flic.kr/p/6Vzzaa
5. Take a break Photo by Kristina Alexadnerson // cc by-nc-nd 2.0 // https://flic.kr/p/cFEcDC • Clear your mind; start fresh • Forget invalid assumptions • Recharge your batteries • Let your subconscious work on it
Four things to walk away with 1. Computers aren’t random, and neither are bugs 2. Persistence will always pay off 3. Don’t be afraid to dive deep 4. Don’t make assumptions or take things for granted Photo by Kristina Alexadnerson // cc by-nc-nd 2.0 // https://flic.kr/p/dvEpfY
Questions? Photo by Marcello Maria Perongini // cc by-nc-nd 2.0 // https://flic.kr/p/6KDtm
Learn More • https://web.duke.edu/cps001/notes/Debugging.pdf • http://www.fiveminutegeekshow.com/20 • http://blog.codeunion.io/2014/09/03/teaching-novices-how-to-debug- code/ • https://www.jetbrains.com/phpstorm/help/debugging.html • http://www.sitepoint.com/debugging-git-blame-bisect/ • http://unix.stackexchange.com/a/50099/80744 • http://codeception.com/docs/01-Introduction • http://chadfowler.com/blog/2014/01/26/the-magic-of-strace/ • http://c2.com/cgi/wiki?RubberDucking Photo by Samantha Marx // cc by 2.0 // https://flic.kr/p/8KrU1R
Thanks! Feedback? • https://joind.in/14752 •@colinodell Photo by Steve Rotman // cc by-nc-nd 2.0 // https://flic.kr/p/xiBK

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Debugging Effectively - php[world] 2015

  • 1. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Debugging Effectively Colin O’Dell
  • 2. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Colin O’Dell • Lead Web Developer at Unleashed Technologies • PHP developer since 2002 • Certifications: Symfony and Magento • PHP League Member • league/commonmark • league/html-to-markdown • PHP 7 Upgrade Guide e-book • @colinodell / www.colinodell.com
  • 3. Overview I. Importance of debugging II. Debugging process III. Tools & Techniques IV. Q&A Photo by Roman Boed // cc by 2.0 // https://flic.kr/p/ngwcf1
  • 4. Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (adjective)
  • 5. Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m important
  • 6. Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m the single most important skill in programming.
  • 7. Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC PlanningCoding
  • 8. Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC Planning Testing & Debugging Coding
  • 9. Debugging is the process of finding and resolving bugs or defects that prevent correct operation of computer software or a system. – Wikipedia Photo by Stephen Dyrgas // cc by-nc-nd 2.0 // https://flic.kr/p/3eTfWU
  • 10. Process is the foundation of effective debugging Process Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa
  • 11. Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa Gain experience with tools and code Experience Process
  • 12. Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa Develop a “sixth sense” “Sixth Sense” Experience Process
  • 13. Junior Developers • Try the “usual” steps • Clear the cache • Re-install dependencies • chmod –R 777 * • Google the error • Try every solution • Ask somebody else • Co-worker • StackOverflow post • Give up Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL
  • 14. XY Problem Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL •I want to solve problem X •How do I solve X?
  • 15. XY Problem Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL •I want to solve problem X •How do I solve X? •Solution Y might work •How can I do Y?
  • 16. Photo by quattrostagioni // cc by 2.0 // https://flic.kr/p/aGjVq8 1.Don’t parse HTML with regex 2.Solve problems the right way
  • 17. “I don’t know why” “For some reason” “Doesn’t make sense” Photo by Stanley Yuu // cc by-nc-nd 2.0 // https://flic.kr/p/pMnfNu
  • 18. Bugs are logical Photo by Photofest
  • 19. “The bug is not moving around in your code, trying to trick or evade you. It is just siting in one place, doing the wrong thing in the same way every time.” – Nick Parlante, Debugging Zen Photo by GrahamC57 // cc by-nc-nd 2.0 // https://flic.kr/p/cwJi9Q
  • 20. Assume your code is the problem Photo by Sergio Flores Rosales // cc by-nc-nd 2.0 // https://flic.kr/p/5UHkaW
  • 21. Systematic Approach 1. Gather information 2. Replicate the issue 3. Identify the culprit 4. Fix it & re-test 5. Mitigate future occurrences Photo from EduSpiral // cc by-nc-nd 3.0
  • 22. 1. Gather information • Expected behavior vs. actual behavior • Error messages • Stack traces Photo from youmustdesireit.wordpress.com •Screenshots •Browser & OS •Date & time •Log entries
  • 23. 2. Replicate the Issue Be able to replicate with 100% certainty Photo by Nick Royer // cc by-sa // https://flic.kr/p/d41ASC
  • 24. 3. Identify the Culprit Photo by U.S. Navy // cc 2.0 // https://flic.kr/p/n6Wgks • Be methodical • Make no assumptions • Understand the bug
  • 25. 4. Fix it & Re-test • Attempt to replicate again • Avoid XY problem • No temporary workarounds! • Add technical debt • May introduce other issues • Never get replaced with true solutions Photo by Jeff Eaton // cc by-sa 2.0 // https://flic.kr/p/b33rSx
  • 26. 5. Mitigate Future Occurrences • Add an automated test • Share your new knowledge • Project documentation • Blog post • StackOverflow • Submit patch upstream Photo by marcokalmann // cc by-nc-nd 2.0 // https://flic.kr/p/4CqLMQ
  • 27. Recap 1. Gather information 2. Replicate the issue 3. Identify the culprit 4. Fix it & re-test 5. Mitigate future occurrences Photo from EduSpiral // cc by-nc-nd 3.0
  • 28. Long-Term Results • Gain experience • Learn how the system works • Build heuristics • Boost confidence Photo by Glenn Beltz // cc by 2.0 // https://flic.kr/p/i7Csdx
  • 29. Tools & Techniques Photo by Alan // cc by-nc-sa 2.0 // https://flic.kr/p/9azLii
  • 30. Two essential tools • Integrated development environment (IDE) • Interactive debugger Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
  • 31. Integrated Development Environment •Minimum features: •Syntax highlighting •Auto-completion •Fast code navigation •Debugger Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
  • 32. Interactive Debugger •Pause code execution •Breakpoints •Conditional breakpoints •Step through execution •Examine variables •Explore call stack Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
  • 34. Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
  • 35. Techniques 1. Trace backwards from known issue 2. Divide & conquer 3. Use tools 4. Get help 5. Take a break Photo by Massmo Relsig // cc by-nc-nd 2.0 // https://flic.kr/p/pFrJCe
  • 36. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 37. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 38. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 39. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 40. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 41. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 42. 2. Divide & Conquer • Identify different code sections • Set breakpoints at the boundaries • Isolate issue to one particular area • Focus efforts on that area
  • 46. ✓ X
  • 48. 3. Use tools • Automated tests • Kint / VarDumper • Debug toolbars • Console utility • Profilers • git bisect •netcat •curl •etc. Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC
  • 49. Automated Tests Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe
  • 50. Kint Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Kint::dump($var);
  • 51. VarDumper Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Twig: {{ dump(foo) }} {% dump foo %} PHP: dump($somevar);
  • 52. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Debug toolbars
  • 53. Console Utility Symfony: app/console Drupal: drush Magento: n98-magerun.phar Laravel: artisan Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe
  • 54. Performance Profiling Identify slowness: • Bottlenecks • Resource hogs • Inefficient code Photo by Alan Stark // cc by-sa 2.0 // https://flic.kr/p/dn3qjx Tools: • Blackfire (freemium) • New Relic (freemium) • xhprof (open-source)
  • 55. Blackfire Photo by Alan Stark // cc by-sa 2.0 // https://flic.kr/p/dn3qjx
  • 56. New Relic Photo by Alan Stark // cc by-sa 2.0 // https://flic.kr/p/dn3qjx
  • 57. git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect start git bisect bad
  • 58. git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect good
  • 59. git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect bad
  • 60. git bisect v1.7 ? ? ? BAD ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect bad
  • 61. git bisect v1.7 ? ? ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect good
  • 62. git bisect v1.7 ? GOOD ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm git bisect good
  • 63. git bisect v1.7 GOOD GOOD ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm
  • 64. git bisect v1.7 GOOD GOOD X BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm abcd123 is the first bad commit
  • 65. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe netcat
  • 66. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe curl
  • 67. 4. Get help • RTFM / RTFD • Project forums or issue queue • StackOverflow, IRC, etc. • Ask a colleague • Expert in that area • Senior developer • Rubber ducking Photo by Hiromitsu Morimoto // cc by-sa 2.0 // https://flic.kr/p/6Vzzaa
  • 68. 5. Take a break Photo by Kristina Alexadnerson // cc by-nc-nd 2.0 // https://flic.kr/p/cFEcDC • Clear your mind; start fresh • Forget invalid assumptions • Recharge your batteries • Let your subconscious work on it
  • 69. Four things to walk away with 1. Computers aren’t random, and neither are bugs 2. Persistence will always pay off 3. Don’t be afraid to dive deep 4. Don’t make assumptions or take things for granted Photo by Kristina Alexadnerson // cc by-nc-nd 2.0 // https://flic.kr/p/dvEpfY
  • 70. Questions? Photo by Marcello Maria Perongini // cc by-nc-nd 2.0 // https://flic.kr/p/6KDtm
  • 71. Learn More • https://web.duke.edu/cps001/notes/Debugging.pdf • http://www.fiveminutegeekshow.com/20 • http://blog.codeunion.io/2014/09/03/teaching-novices-how-to-debug- code/ • https://www.jetbrains.com/phpstorm/help/debugging.html • http://www.sitepoint.com/debugging-git-blame-bisect/ • http://unix.stackexchange.com/a/50099/80744 • http://codeception.com/docs/01-Introduction • http://chadfowler.com/blog/2014/01/26/the-magic-of-strace/ • http://c2.com/cgi/wiki?RubberDucking Photo by Samantha Marx // cc by 2.0 // https://flic.kr/p/8KrU1R
  • 72. Thanks! Feedback? • https://joind.in/14752 •@colinodell Photo by Steve Rotman // cc by-nc-nd 2.0 // https://flic.kr/p/xiBK

Editor's Notes

  • #3: PHP developer 13 years JS, Java, C#
  • #5: What are some words For me: fun challenge
  • #7: Take this one step further Why is that?
  • #8: How much time coding? 2/3rds
  • #9: According to the Mythical Man Month, 1/6th ½ is testing/debugging How much - actually writing code vs getting it working Area where it’s worthwhile to become efficient
  • #10: READ SLOWLY Shouldn’t be done haphazardly
  • #13: Immediate understanding of what type of problem, where it might be Like intuition, but not Understanding without proof, but based on logic and experience -- Focus on the process Experience and “sixth sense” will come with time NEXT: Debugging process
  • #14: And intermediate developers BE NICE / CONSTRUCTIVE
  • #15: TODO ADD NOTES
  • #16: When you give up on the proper approach Apply workaround instead Improper solutions will cause issues later NEXT - EXAMPLE
  • #17: First Magento client Ability to generate PDFs Base85-encoded Don’t be clever TRANSITION NEEDED!!
  • #18: Magical thinking Code is not a magic black box
  • #20: Article sneaky
  • #21: Bugs are almost always based on faulty assumptions If you build on faulty assumptions 95% in your code If helping others, assume their code is problem Challenge their assumptions Take with grain of salt
  • #23: Define the symptoms Collect everything you can
  • #24: Automated tests preferred, but manual is okay too LEGOS
  • #25: Understand the fundamental nature Exactly why We’ll get into the tools & techniques
  • #32: Other nice-to-haves: File syncing Git integration Run tools PhpStorm, Sublime Text, vim NOT Notepad++ or Dreamweaver
  • #33: Debuggers are awesome tool … Better than primitive approaches Examine in real time Xdebug Chrome developer tools
  • #34: Click 4 times Dive in Look at call stack
  • #35: Advanced breakpoints ============== Conditions Grouping
  • #37: Stack trace Grep for error message Set breakpoint For example
  • #38: Examine variables How did I get here? – call stack
  • #49: Debugger is critical Not only tool Tools are not a substitute for thinking
  • #50: Phpunit Phpspec behat
  • #51: Drop-in replacement for var_dump(), print_r() and debug_backtrace().
  • #52: Symfony VarDumper component Works in Twig, PHP, CLI, etc. Better than vardump Handles: - Circular references - Deeply-nested objects Public vs protected vs private Custom casters to change representation
  • #58: Q: How many people here are using Git? Familiar with Git bisect? Built-in tool Assists with running a binary search across your commits
  • #65: Scales logarithmically – runs in O(log N) 9 commits - 4 tests 10x: 90 commits – 8 tests 100x: 900 commits - 16 tests
  • #68: Fourth technique
  • #70: 1. There is ALWAYS a logical explanation 3. Great learning opportunity 4. Challenge everything
  • #71: ? Other Questions? Talk afterwards or contact me
  • #73: Thank you guys I’d appreciate feedback