ZF-5812: Zend_Db_Select __toString() should cast its return to string
Even if we know that the return of __toString is a string, it's not in one particular use-case :
echo new Zend_Db_Select($db);
In that use case, the select object is empty of any value, resulting in echoing nothing, and __toString() complains about that : Catchable fatal error: Method Zend_Db_Select::__toString() must return a string value in xxxx
I suggest just to cast the return of __toString() to string.