This is used to assign()
values to the templates by reference instead of
making a copy. See the PHP manual on variable referencing for an explanation.
Technical Note:
This is used to assign values to the templates by reference.
If you assign a variable by reference then change its
value, the assigned value sees the change as well. For
objects,
assign_by_ref() also avoids an in-memory copy of the assigned object.
See the PHP manual on variable referencing for an in-depth
explanation.