Upgrading Legacy to the Latest PHP Version

Your application runs on an old PHP version that is about to go out of support. How to upgrade without breaking the application? You will need the right tools for detecting and fixing those issues, as well as a way to verify that the application is still working correctly. In this presentation, I will share the strategy that I employed when upgrading millions of lines of untested code.

Transcript

1. Upgrading Legacy to the
   Latest PHP Version
   IPC MUNICH | OCT 28, 2021 @afilina
   

   View Slide

2. "I don't know whether my application
   works on the latest PHP."
   

   View Slide

3. • Check compatibility.
   • Fix issues.
   • Test the fixes.
   

   View Slide

4. Anna Filina
   • Coding since 1997 (VB4)
   • PHP since 2003
   • Legacy archaeology
   • Test automation
   • Public speaking
   • Mentorship
   • YouTube videos
   

   View Slide

5. Docker image
   PHPCO
   PHPCompatibility
   

   View Slide

6. phpco() { docker run --init -v $PWD:/mnt/src:cached --rm -u "$(id
   -u):$(id -g)" frbit/phpco:latest $@; return $?; }
   

   View Slide

7. phpco -p --colors --extensions=php --runtime-set testVersion 7.4 .
   

   View Slide

8. FILE: /mnt/src/app/controllers/MyController.php
   ------------------------------------------------------------------
   FOUND 1 ERROR AFFECTING 1 LINE
   ------------------------------------------------------------------
   166 | ERROR | Using 'break' outside of a loop or switch structure
   | | is invalid and will throw a fatal error since PHP
   | | 7.0
   ------------------------------------------------------------------
   

   View Slide

9. public function myFunction($result)
   {
   if ($result == null) {
   break;
   }
   }
   

   View Slide

10. public function myFunction($result)
    {
    if ($result == null) {
    return;
    }
    }
    

    View Slide

11. PHPCompatibility
    tells us what to fix.
    

    View Slide

12. Fixing
    

    View Slide

13. $response = '1234567890';
    $header = 'Content-length: ' . strlen($response) + 1;
    echo $header;
    

    View Slide

14. 3v4l.org
    

    View Slide

15. View Slide

16. View Slide

17. View Slide

18. $response = '1234567890';
    $header = 'Content-length: ' . (strlen($response) + 1);
    echo $header;
    

    View Slide

19. Function each() is deprecated since PHP 7.2;
    Use a foreach loop instead
    

    View Slide

20. while (list($i, $row) = each($result))
    foreach ($result as $i => $row)
    

    View Slide

21. $i = each($result)['key'];
    $v = each($result)['value'];
    $i = each($result)[0];
    $v = each($result)[1];
    

    View Slide

22. $a = each($result);
    $b = each($result);
    

    View Slide

23. else if (list(, $optArg) = each($args))
    

    View Slide

24. final class Php56Compatibility
    {
    public static function each(array &$array)
    {
    if (current($array) === false) {
    return false;
    }
    $key = key($array);
    $value = current($array);
    next($array);
    return [
    1 => $value,
    'value' => $value,
    0 => $key,
    'key' => $key,
    ];
    }
    }
    

    View Slide

25. Portable, unit-tested solution
    wrapped in a class.
    

    View Slide

26. We can clean things up at a later time
    (technical debt).
    

    View Slide

27. mcrypt
    PHP
    

    View Slide

28. mcrypt
    PECL
    PHP
    

    View Slide

29. mcrypt
    PECL
    PHP
    libmcrypt
    

    View Slide

30. PHP
    openssl
    

    View Slide

31. mcrypt.OFB != openssl.OFB
    

    View Slide

32. How to test mcrypt to openssl upgrade?
    

    View Slide

33. • Can we decrypt what we just encrypted?
    • Can we decrypt what we already have in our
    database?
    

    View Slide

34. encrypted
    App with mcrypt
    original
    

    View Slide

35. public function testCanDecrypt()
    {
    //...
    $decrypted = $security->decrypt($encrypted);
    self::assertEquals($original, $decrypted);
    }
    

    View Slide

36. mysql_
    mysqli_
    PDO
    

    View Slide

37. • Connection object needs to be available.
    • Connection object now a mysqli type.
    • Field metadata represented differently.
    • Different methods for unbuffered queries.
    

    View Slide

38. mysql to mysqli conversion
    can't be unit-tested.
    

    View Slide

39. mysql_connect
    mysql_query
    mysql_close
    mysqli_connect
    mysqli_query
    mysqli_close
    $connection
    

    View Slide

40. /login
    redirect to profile
    credentials
    session
    database
    encryption
    

    View Slide

41. /login
    redirect to profile
    credentials
    POST /login
    Redirect URL
    

    View Slide

42. $response = $this->guzzle->send($request);
    self::assertEquals(/**/);
    

    View Slide

43. You can use this approach
    to test the entire application.
    

    View Slide

44. PHPCO won't detect everything.
    

    View Slide

45. class MyClass extends BaseClass
    {
    public function validate($field, $value)
    {
    //...
    }
    }
    class BaseClass
    {
    public function validate(string $field, $value, $message = null)
    {
    //...
    }
    }
    

    View Slide

46. View Slide

47. • Start testing.
    • Note the errors that appear.
    • Tune static analysis for those specific errors.
    

    View Slide

48. Write more tests.
    

    View Slide

49. var_dump(0 == "");
    

    View Slide

50. View Slide

51. What about the framework?
    

    View Slide

52. • New framework might be too different.
    • Is there a fork that keeps up with PHP?
    

    View Slide

53. You could make the framework compatible.
    

    View Slide

54. What about the tests?
    

    View Slide

55. • Is PHPUnit compatible with PHP?
    • Can it be updated?
    • Might need to upgrade PHPUnit.
    

    View Slide

56. Do not fix your tests and code
    at the same time.
    

    View Slide

57. /login
    redirect to profile
    credentials
    POST /login
    Redirect URL
    

    View Slide

58. Tests
    PHP 8.0
    PHP 5.4 Application
    

    View Slide

59. Tests
    PHP 8.0
    PHP 8.0 Application
    

    View Slide

60. • Use PHPCompatibility
    • Use Psalm, PHPStan, etc.
    • Don't be afraid to fix the framework/libs.
    • Write tests.
    

    View Slide

61. @afilina
    Questions?
    

    View Slide