In Pennsylvania, you may have a case against the dog owner. The owner has a duty to keep his dog under proper and adequate control pursuant to Pennsylvania's "leash law." The dog needs to be confined to an owner’s property or maintained within reasonable control of the owner or another person.
In this case, if the gate was not properly maintained and allowed the dog to escape, you may have a claim. However, further inquiry regarding the facts of your case and investigation or inspection of the gate are needed.
Therefore, it is important that you speak to an experienced Pennsylvania dog bite lawyer about the injuries you suffered as a result of the dog attack.