No Self Referencing Constants¶
It is not possible to define a recursive PHP class constant, although it is possible to write it. A self referencing constant may be with itself, or it may use a complex right of class definitions before failing.
There is a dedicated PHP error message for this situation: ‘Cannot declare self-referencing constant’.
One fun aspect is that the is not detected at compilation time, but at execution time, when the constant is actually used. The problem may lie dormant for a long time before revealing itself.
The error is also moved by other reported when several constants are compounded to build one, in a cyclic fashion.