Presentation I held internally at Bigpoint about what the main problem with Singleton, especially in PHP, is.

1. The Singleton Dilemma
Frank Sons
Senior PHP Engineer CTD

2. The Singleton Dilemma
What is a Singleton?
What is the problem?
What is the solution to this dilemma?
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3. Singleton? What‘s that?
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4. Singleton? Tell me more…
Probably best known design pattern
Only one instance of a class at any time
Global access to that single instance
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5. How to implement a Singleton in PHP?
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6. How to use the Singleton?
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7. So, it is really cool, isn‘t it?
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8. Singleton and PHP are no friends
Singleton: unique instance for application
PHP: Shared-Nothing architecture
Dilemma: instance only unique for request
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9. Singleton has even more problems
Dependency hiding
Globals are bad, singleton is a global
No Unit Testing possible
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10. Is there a solution?
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11. Solution: Just create one!
Code Convention: just create one
Trust your Team members!
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12. Solution: Dependency Injection
Create one instance and „inject“ it
Don‘t create objects in regular classes
Objects should be loosely coupled
„Ask, don‘t look“
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13. Solution: Dependency Injection
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14. Solution: Factory
Encapsulates object creation
Handles object lifetimes
Different factories for different lifetimes
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15. Solution: Factory
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16. Solution: PHP application lifetime
Cache or Session for „application“ lifetime
Factory can handle Cache or Session
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17. „Friends don‘t let friends do Singleton“
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18. Benefits!
Unit Testing is possible!
Better lifetime handling!
Easy object creation!
Easy to change dependencies!
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19. And about the good Singleton…
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20. The only good Singleton…
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21. Thank you!
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22. Bigpoint GmbH
Frank Sons
Senior Software Engineer CTD
Drehbahn 47-48
20354 Hamburg
Germany
Tel +49 40.88 14 13 - 0
Fax +49 40.88 14 13 - 11
info@bigpoint.net
www.bigpoint.net
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