@beberlei it shares the same content for all calls of this method (for all instances). This can be interesting when you have a big array in it to save memory in a method called often. But here, it does not have any benefit:

- the method will generally be called only once, so you loose all benefits
- this string does not consume much memory so there is no clear win. Thus, it would be garbage collected at the end of the method anyway as you don't keep references to it elsewhere
- making it static forces PHP to keep it in memory until the end of the process (like for static properties of a class) as it is shared between all calls, so it actually hurts the garbage collector instead of helping here.

This is a case where you are actually hurting the GC while trying to be smarter than PHP and failing.