This statement does not serve a purpose anymore.
In a long forgotten world it indicated the main version number of PHP which the code in the file was compatible to.
http://pear.php.net/manual/en/standards.sample.php
But since PHP 5.1 and later this is only marginally true.
Thus I propose to remove it from CakePHP.
In 2.1, the default value was null, which does not impart any behavior.
In 2.2 this was changed to false, which makes it hard to validate ''
with validation methods. Move some tests around and update tests that
probably should have been failing before.
Fixes#2983
