Class II. One of the officials of the municipality, other than a member of the governing body, to be appointed by the Mayor, provided that if there is an Environmental Commission, the member of the Environmental Commission who is also a member of the Planning Board, as required by N.J.S.A. 40:56A-1, shall be a Class IV Planning Board member, unless there be among the Class IV or alternate members of the Planning Board both a member of the Zoning Zoning Board of Adjustment or Historic Preservation Commission and a member of the Board of Education, in which case the member common to the Planning Board and Municipal Environmental Commission shall be deemed a Class II member of the Planning Board. For the purpose of this section, membership on a municipal board or commission whose function is advisory in nature, and the establishment of which is discretionary and not required by statute, shall not be considered the holding of municipal office.