43 Pa. Stat. § 206j
No temporary restraining order or temporary injunction shall be issued in any case involving or growing out of a labor dispute, except on condition that complainant shall first file an undertaking with adequate security, in an amount to be fixed by the court, sufficient to recompense those enjoined for any loss, expense or damage caused by the improvident or erroneous issuance of such order or injunction, including all reasonable costs (together with a reasonable attorney's fee), and expense of defense against the order, or against the granting of any injunctive relief sought in the same proceeding and subsequently denied by the court.
The undertaking herein mentioned shall be understood to signify an agreement entered into by the complainant and the surety, upon which a decree may be rendered in the same suit or proceedings against said complainant and surety upon a hearing to assess damages, of which hearing complainant and surety shall have reasonable notice, the said complainant and surety submitting themselves to the jurisdiction of the court for that purpose. But nothing herein contained shall deprive any party having a claim or cause of action under or upon such undertaking from electing to pursue his ordinary remedy by suit at law or in equity.
43 P.S. § 206j