The offensive tackle from Oklahoma was selected fourth overall in April. He was the last of Philadelphia's draft picks to agree to terms in the deal announced Saturday night.
The 6-foot-6, 303-pound Johnson was the third tackle drafted among the first four picks. He was a quarterback in high school and went to Oklahoma as a tight end. Johnson switched to defensive end in 2010 and then moved to the offensive line because of injuries. He started at right tackle in 2011 and left tackle last year.