Have you ever extended legacy code? What is legacy code? How to work with legacy? During this talk I'd like to explain what's a legacy code, how to improve it, and show you how to progressively migrate your project to modern concepts.

1. HOW TO WORK WITH
LEGACY CODE

2. MICHAŁ SZCZUR
PHP Developer since 2010
bass guitarist and trumpeter
michalszczur.pl
Created by /Michał Szczur @partikus

3. AGENDA
Scope explanation
Dive into legacy mess
How to start and not die
Step by step to heaven

4. THANKS TO MAREK MATULKA
WHO INSPIRED ME!

5. WHAT IS LEGACY CODE?

6. CODE WRITTEN MANY YEARS AGO
BY MYSELF OR OTHER NINJAS

7. LOW QUALITY CODE

8. (PRE)HISTORICAL CODE USES NONEXISTING
FRAMEWORKS/LIBRARIES

9. NO ENVIRONMENT SEPARATION

10. NO TESTS !!!

11. WHEN CODE CAN BE CALLED
LEGACY ???

12. WHEN IT IS
UNMANAGED

13. WHEN IT IS
TOO BUGGY

14. WHEN IT IS
TOO HARD TO UNDERSTAND

15. WHEN IT IS
NONUPGRADABLE

16. WHEN IT IS
UNDEBUGGABLE

17. WHEN IT IS
UNREADABLE

18. WHEN IT IS
TOO COUPLED TO FRAMEWORK

19. WHEN IT IS
TOO HARD TO ADD NEW FEATURE

20. WHAT IS NEXT?

21. FIGHT OR DIE

22. NO !!!
WE'RE NINJA DEVS
WE LOVE CHALLENGES

23. LET'S DO IT!

24. TAKE NEW FRAMEWORK
AND START FROM THE BEGINNING

25. :(MAYBE SOME DAY IN THE FUTURE

26. WHAT IS NEXT?

27. LET'S REFACTOR

28. BUT WHY ???

29. EXTENDED LEGACY
CODE
WEB PHP APP

30. PREASUMPTIONS
YOU DON'T KNOW BUSINESS LOGIC
MOSTLY PROCEDURAL CODE
NO SEPARATION, JUST A FEW LARGE FILES
YOU NEED TO CHANGE STH

31. ANALYZE

32. COVER
IT MEANS WRITE TESTS

33. WHAT SHOULD WE
TEST?

36. WHY SHOULD WE WRITE TESTS?

37. LOW LEVEL DOCUMENTATION
FEATURES DESCRIBED BY SCENARIOS (E.G.
GHERKIN)
CLEAN CODE
EASY TO CHANGE (LESS PAIN)
EASY CONTINUOUS DEPLOYMENT

38. START REFACTORING

39. # Project structure
/404.php
/database.php
/functions.php
/index.php
/page.php

40. PROCEDURAL CODE
WRITTEN IN PHP
INLINE PHP FUNCTIONS MIXED WITH HTML,CSS,JS

41. #/functions.php
function show_all() {
$db = connect_to_db();
$sql = 'SELECT * FROM receivers';
$result = mysql_query($sql) or die(mysql_error());
while ($row = mysql_fetch_array($result)) {
//echo 'ID: ' . $row['id'] . ', mail: ' . $row['mail'];
echo ''.$row['mail'].'';
echo '<form id="'.$row['id'].'" name="n_ID" method="POST" action=
<input type="hidden" name="id" value="'.$row['id'].'" />
<input type="submit" name="delete" value="Delete" />
</form>';
}
if (isset($_POST['delete'])) {
$n_ID = $_POST['id'];
$sql = "DELETE FROM receivers WHERE id = $n_ID";
mysql_query($sql) or die(mysql_error());

42. WRITE FUNCTIONAL
TEST

43. // show_all_receivers.js
casper.test.begin('List all receivers', 5, function suite(test) {
casper.start("http://myapp.dev/mailsender.php", function() {
test.assertHttpStatus(200);
test.assertTitle("Homepage | Mail Sender", "Homepage title is expecte
});
casper.thenClick('a#show-all', function() {
test.assertHttpStatus(200);
test.assertTitle(
"Receivers list | Mail Sender",
"Page title is correct"
);
});
casper.run(function() {
test.done();
});
});

44. PROCEDURAL CODE??
YOU NEED STH MORE

45. IOC
INVERSION OF CONTROL

46. DEPENDENCY
INJECTION
IOC IMPLEMENTATION

47. DON'T REINVENT THE
WHEEL

48. PACKAGE MANAGER
COMPOSER
RUBYGEMS
MAVEN

49. COMPONENTS
DEPENDENCY INJECTION
/ /SYMFONY DI PIMPLE AURA DI

50. WHY SYMFONY
COMPONENTS?

51. WELL TESTED

52. DECOUPLED

53. REUSABLE

54. WELL DOCUMENTED
AND KNOWN BY COMMUNITY

55. NEXT STEP IS...

56. MOVE APP TO /WEB/
# new project structure
/
/web/404.php
/web/database.php
/web/functions.php
/web/index.php
/web/page.php

57. INSTALL COMPOSER
php -r "readfile('https://getcomposer.org/installer');" > composer-setup.php
php -r "if (hash('SHA384', file_get_contents('composer-setup.php')) ===
php composer-setup.php
php -r "unlink('composer-setup.php');"

58. INIT COMPOSER CONFIG IN THE ROOT DIR
php composer.phar init

59. PROJECT STRUCTURE
ls -l
/
/composer.json
/web/

60. COMPOSER.JSON
{
"name": "michalszczur/legacy-demo",
"authors": [
{
"name": "Michal Szczur",
"email": "job@michalszczur.pl"
}
],
"require": {},
"autoload": {
"psr-4": {
"": "src/"
}
},
"description": "Legacy app demo",
"type": "project",
"license": "proprietary"

61. ADD DEPENDENCIES
php composer.phar require symfony/dependency-injection
php composer.phar require symfony/config
php composer.phar require symfony/yaml

62. <?php
# /web/container.php
use SymfonyComponentDependencyInjectionContainerBuilder;
use SymfonyComponentConfigFileLocator;
use SymfonyComponentDependencyInjectionLoaderYamlFileLoader;
require __DIR__.'/../vendor/autoload.php';
$container = new ContainerBuilder();
$loader = new YamlFileLoader($container, new FileLocator(__DIR__.'/../app/con
$loader->load('services.yml');
$container->compile();

63. WHICH SERVICES DO WE REALLY
NEED?

64. function show_all()
{
# Database connection needed
$db = connect_to_db();
$sql = 'SELECT * FROM mail_sender';
$result = mysql_query($sql) or die(mysql_error());
//...

65. CREATE SEVICES.YMLDEFINITION

66. SERVICES.YML
parameters:
db_host: localhost
db_port: 3306
db_name: legacyapp
db_user: myuser
db_pass: mypass
services:
db:
class: PDO
arguments: ['mysql:port=%db_port%;host=%db_host%;dbname=%db_name%'
receiver_repository:
class: PDOReceiverRepository
arguments: ['@db']

67. USE CONTAINER AND REPOSITORY

68. #index.php
...
require 'container.php';
...
function show_all()
{
# Database connection needed
$receiverRepository = $container->get('receiver_repository');
$result = $receiverRepository->findAll();
...

69. #index.php
...
$result = $receiverRepository->findAll();
foreach ($result as $row) {
echo ''.$row['mail'].'';
echo '<form id="'.$row['id'].'" name="n_ID" method="POST" action="mai
<input type="hidden" name="id" value="'.$row['id'].'" />
<input type="submit" name="delete" value="Usuń" />
</form>';
}
...

70. PHP ~ HTML
STILL MIXED TOGETHER

71. TWIG
TEMPLATE ENGINE FOR PHP

72. INSTALL TWIG USING COMPOSER
php composer.phar require twig/twig

73. SERVICES.YML
parameters:
...
twig_paths:
- app/Resources/views
services:
...
twig.loader:
class: Twig_Loader_Filesystem
arguments: ['%twig_paths%']
twig:
class: Twig_Environment
arguments: ['@twig.loader']

74. #index.php
...
$twig = $container->get('@twig');
$result = $receiverRepository->findAll();
echo $twig->render(
'receiver_list.html.twig',
['receivers' => $result]
);
...

75. {% for receiver in receivers %}
<form id="{{ receiver.id }}" name="n_ID" method="POST" action="mail_sender.ph
<input type="hidden" name="id" value="{{ receiver.id }}" />
<input type="submit" name="delete" value="Delete" />
</form>
{% endfor %}

76. BEFORE
function show_all()
{
$db = connect_to_db();
$sql = 'SELECT * FROM mail_sender';
$result = mysql_query($sql) or die(mysql_error());
while ($row = mysql_fetch_array($result)) {
//echo 'ID: ' . $row['id'] . ', mail: ' . $row['mail'];
echo ''.$row['mail'].'';
echo '<form id="'.$row['id'].'" name="n_ID" method="POST" action="mai
<input type="hidden" name="id" value="'.$row['id'].'" />
<input type="submit" name="delete" value="Usuń" />
</form>';
}
...
mysql_free_result($result);
mysql_close($db);
}

77. AFTER
function show_all() {
$receiverRepository = $container->get('receiver_repository');
$twig = $container->get('@twig');
$result = $receiverRepository->findAll();
echo $twig->render(
'receiver_list.html.twig',
['receivers' => $result]
...
);

78. LET'S SUM UP

79. COMMUNICATION

80. ANALYZE

81. TESTS

82. SMALL STEPS

83. NOT EVERYTHING SIMUNTANOUSLY

84. PACKAGE MANAGER

85. DEPENDENCY INJECTION

86. THIRD PARTY LIBRARIES

87. DESIGN PATTERNS

88. SOLID

89. DECOUPLE

90. TESTS

91. QUESTIONS?
SLIDES: SLIDESHARE.NET/MICHASZCZUR
FEEDBACK: JOIND.IN/EVENT/CODETECON-20161
TWITTER: @PARTIKUS
HOMEPAGE: MICHALSZCZUR.PL

92. THANKS!

93. LINKS
Marek Matulka - Modernising the Legacy
CasperJS
Symfony Components
Working Effectively with Legacy Code by Michael Feathers
Page Object Pattern (Martin Fowler)
Page Object Pattern (Selenium Docs)