This document provides an overview of intermediate object-oriented programming concepts in PHP, including magic methods, polymorphism, collections, filtering collections, and the SPL iterator. Magic methods allow objects to intercept method calls and property access, such as __construct, __destruct, __call, __get, __set and more. Polymorphism allows code to use different objects in the same way through interfaces. Collections and the iterator pattern are demonstrated using a SilverwareDrawer class. Loose coupling and high cohesion principles are also discussed.

1. vivat ad codicem, code vivere
Intermediate OOP in
PHP
Open West - May 8, 2015
David Stockton
@dstockto

2. What we’ll cover
❖ Magic Methods
❖ Polymorphism
❖ Collections
❖ Filtering Collections
❖ SPL Iterator

3. What we’ll cover
❖ SPL Count
❖ SPL ArrayAccess
❖ Listener Pattern
❖ Loose Coupling
❖ High Cohesion

4. Magic Methods
❖ Methods all start with __

5. __construct & __destruct
❖ __construct is called when you new up an object
❖ Initialize object properties
❖ Don’t do work!
❖ __destruct is called when an object goes out of scope
❖ Shut down connections, cleanup work

6. __call
❖ __call($name, array $arguments)
❖ Method called when method is called that is not in
scope
❖ Method doesn’t exist
❖ Method is private / protected and called from outside
object

7. __call

8. __callStatic
❖ Just like __call but for static calls out of scope
❖ Foo::createFromThing()

9. __get, __set, __isset, __unset
❖ In many cases, if you need one, you need them all
❖ Weird bugs if you don’t implement them all

10. __get
❖ __get($name)
❖ Called when reading an object property that’s not in
scope
❖ $value = $foo->madeUpValue;

11. __get

12. __set
❖ __set($name, $value)

13. So, why do we need them all?
❖ $foo->bar = ‘baz’;
❖ $value = $foo->bar; // Get baz
❖ if (isset($foo->bar)) {
$value = $foo->bar; // Never get here if no __isset
}

14. __isset
❖ __isset($name)
❖ isset($object->variable)

15. __unset
❖ __unset($name)
❖ unset($object->variable);

16. What you can do with them
❖ Implement a class that doesn’t allow dynamic
properties
❖ Implement a class that only allows properties with
certain naming conventions
❖ Automatic calling of accessors (getters and setters)

17. The downsides
❖ Harder to follow, no “ctrl-click” in IDEs
❖ No auto-complete for __call or __callStatic methods in
IDEs
❖ Can use @method doc block to help
❖ @method int add() add(numeric $a, numeric $b) Add numbers

18. @method docblock

19. __sleep & __wakeup
❖ Called on serialize() and unserialize() calls
❖ __sleep: Use to close connections, cleanup
❖ __wakeup: Use to re-establish connections, setup
❖ Why?
❖ Some things in PHP are not serializable

20. __toString()
❖ Retrieve string representation of a class
❖ Must return a string
❖ Cannot throw an exception

21. __toString

22. __toString

23. __clone
❖ Create a new object based on an existing object
❖ Called when clone is used:
❖ $foo = clone $bar;

24. __clone
❖ By default, clone is
shallow

25. $foo = new Foo();
Foo$foo
Foo
$bar$foo Bar

26. $foo2 = clone $foo;
Foo
$bar$foo Bar
Foo
$bar$bar

27. Now with __clone

28. $foo = new Foo();
Foo$foo
Foo
$bar$foo Bar

29. $foo2 = clone $foo;
Foo
$bar$foo Bar
Foo
$bar$bar
__clone called on the clone

30. $foo2 = clone $foo;
Foo
$bar$foo Bar
Foo
$bar$bar Bar

31. __invoke
❖ Allows an object to be used like a function or callable
❖ Object can be built configured and then “executed”

32. __invoke

33. __invoke

34. __autoload
❖ Don’t use __autoload, use spl_autoload_register
❖ Called when a class, interface, or trait is used that hasn’t
been loaded
❖ Allows just in time loading of classes, no more requires
and includes at the top of files

35. __set_state
❖ Used with var_export
❖ Allows setting of object variables from an array of input

36. __debugInfo
❖ New in PHP 5.6
❖ Controls output of var_dump

37. __debugInfo

38. var_dump

39. Add __debugInfo

40. var_dump again

41. Vah arietem ovem
Polymorphism
Allow code to use different objects in the
same way

42. Speakable interface

43. Polymorphism

44. Polymorphism

45. omnia et singula ibi in suo
Collections and
Polymorphism

46. Silverware Drawer

47. lambens catini, mundatis
SilverwareContainer interface

48. cur non utamur cædentes ligna
Silverware interface

49. Abstract Utensil Class
“Type a quote here.”

50. A Forking Example

51. Silver Spoons

52. Knife

53. Put silverware away

54. How many utensils?
❖ Add method getNumberOfItems
❖ Implement SPL Countable
- OR

55. SPL Countable

56. How to use?

57. Retrieve Specific Utensils

58. SPL to the Rescue
❖ Implement SPL ArrayAccess
❖ Make our object work like an array

59. SPL ArrayAccess

60. SPL ArrayAccess

61. furca in perscriptorem
What does that
allow?

62. Use an iterator:
• Implement iterator
• Extend one of these:
• AppendIterator
• ArrayIterator
• CachingIterator
• CallbackFilterIterator
• InfiniteIterator
• …etc.

63. Easy way Extend ArrayIterator

64. Add some silverware

65. Now what? Iterate it!

66. A new iterator

67. Only get clean utensils

68. Sed quis custodiet ipsos vigil
SPLSubject /
SPLObserver
Moving right along

69. Implement SplSubject

70. Email class continued

71. Validate uses our observers

72. Build some observers Invalid Emails don’t send

73. Limit Sends by
domains?

74. Put it all together

75. Loose Coupling

76. Loose Coupling
❖ Minimize number of hard-coded dependencies
❖ Type hint interfaces, not classes
❖ Dependency Injection / Inversion of Control

77. Dependency Injection Simply

79. High Cohesion
Do one thing well

80. High Cohesion
❖ Do one thing well
❖ Methods
❖ Classes
❖ Packages / Namespaces
❖ Everything the class does is related to the goal

81. –David Stockton
“If you have to use ‘and’ to describe what your
method or class does, it’s probably doing too
much.”

82. Prefer Composition
over Inheritance

83. Prefer Composition over Inheritance
❖ Inheritance is not the only way to expand functionality
of a class
❖ Often it’s not even the best way

84. Prefer Composition over Inheritance
❖ Compose classes with other classes
❖ Let objects defer to others to do the work
❖ Use dependency injection to get inner classes

85. Photo Credits
• Lego Magician - https://www.flickr.com/photos/evaysucamara/5438832695
• Silverware - https://www.flickr.com/photos/jenny-pics/4128947072
• Fork - https://www.flickr.com/photos/naturesdawn/2507321223
• Trailer hitch - https://www.flickr.com/photos/jeremybrooks/2476396242
• The Glue Side of the Force - https://www.flickr.com/photos/st3f4n/4085958000
• Last Will and Testament - https://www.flickr.com/photos/ken_mayer/5599532152
• Guest Composer - https://www.flickr.com/photos/tamuc/12843465194

86. Please rate this talk:
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