(a) The governing body of any Class 6 municipality may determine by ordinance that the planning commission of the municipality, created under authority of Section 11-52-3, shall consist of seven voting members appointed as follows:
(1) Six members appointed by the mayor.
(2) One member, appointed by a majority of the city council, who may be a member of the city council.
(b) In addition, one nonvoting advisory member shall be appointed by the mayor, who shall be a senior administrative official of the municipality qualified by education, training, experience, and job responsibilities to provide substantive and technical advice, assistance, and guidance to the planning commission in the exercise of its statutory functions.
(c) All members of the planning commission shall be at least 21 years of age and, to the extent not inconsistent with this section, shall meet the additional qualifications for membership on municipal planning commissions as prescribed by law.
(d) All voting members of the planning commission shall be residents of the municipality. A vacancy shall be declared by the planning commission, after notice to the member, if a voting member of the planning commission ceases to reside in the municipality. The vacant position shall be filled by the mayor or council, as appropriate, within 90 days of a declaration of vacancy by the planning commission. The declaration of a vacancy shall operate to terminate the membership and voting authority of the member who no longer resides within the municipality.