Philip preached the gospel in Samaria.

What did Philip preach?

Philip preached Christ unto them, the kingdom of God, and the name of Jesus.

"Then Philip went down to the city of Samaria, and preached Christ unto them." - Acts 8:5 KJV

"But when they believed Philip preaching the things concerning the kingdom of God, and the name of Jesus Christ, they were baptized, both men and women." - Acts 8:12 KJV

The people received the gospel message Philip preached to them, were baptized in Jesus name, but they weren’t receiving the gift of the Holy Ghost.

Water baptism in Jesus name and the baptism of the Holy Ghost are two separate and distinct experiences.

"Now when the apostles which were at Jerusalem heard that Samaria had received the word of God, they sent unto them Peter and John: who, when they were come down, prayed for them, that they might receive the Holy Ghost: (for as yet he was fallen upon none of them: only they were baptized in the name of the Lord Jesus.) Then laid they their hands on them, and they received the Holy Ghost." - Acts 8:14-17 KJV

Now the people had fully obeyed the gospel. They repented of their sins, they were baptized in Jesus name for the remission of sins, and they received the gift of the Holy Ghost. Just like Peter preached on the Day of Pentecost.

"Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost." - Acts 2:38 KJV

"For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call." - Acts 2:39 KJV