This is necessary because the XMI generated by PEAR PHP UML does not integrate with the MagicDraw UML code engineering sets system, one can however import the XMI (into the design packages).
It is best not to put a single element, not a diagram, no relationships, nothing, that changes the design(ed) packages ! Instead, you use analysis diagrams, under the '@' analysis package root, to pull in design elements where appropriate.