53 Pa. Stat. § 23434
No officer or officers, having the power of appointment to, or employment in, the civil service of any city of the second class, shall after the first day of July, one thousand nine hundred and seven, select or appoint any person for appointment, employment, promotion, or reinstatement except in accordance with the provisions of this act and the rules and regulations prescribed thereunder: Provided, That the power of the mayor to appoint special policemen in times of emergency or riot, as provided in article three, section one, of the act of March seventh, one thousand nine hundred and one, entitled "An act for the government of cities of the second class," as amended by the act of April twenty-three, one thousand nine hundred and three, entitled "An act changing the title of the chief executive officer in cities of the second class from recorder to mayor," shall remain as heretofore.
53 P.S. § 23434