• Context
• Strategy
• Concrete Strategy

To separate strategies and to enable fast switching between them. Also this pattern is a good alternative to inheritance (instead of having an abstract class that is extended).

• sorting a list of objects, one strategy by date, the other by id
• simplify unit testing: e.g. switching between file and in-memory storage

You can also find these code on GitHub

ObjectCollection.php

.. literalinclude:: ObjectCollection.php
   :language: php
   :linenos:

ComparatorInterface.php

.. literalinclude:: ComparatorInterface.php
   :language: php
   :linenos:

DateComparator.php

.. literalinclude:: DateComparator.php
   :language: php
   :linenos:

IdComparator.php

.. literalinclude:: IdComparator.php
   :language: php
   :linenos:

Tests/StrategyTest.php

.. literalinclude:: Tests/StrategyTest.php
   :language: php
   :linenos: