According to Jeff Wilson on Twitter, the Rangers and Matt Harrison have agreed to a five year, $55 million contract with an option for a sixth year.
Harrison was scheduled to be a free agent after the 2014 season. After making $2.95 million in 2012, Harrison was expected to make around $6.5 million in 2013 as a second-year arbitration-eligible player.
Given that, I'd guess right now that Harrison will make around $6.5 million in 2013, $9.5 million in 2014, and then $13 million per year for 2015-17, with the club option for 2018 at around $15 million or so.
Harrison, part of the package the Rangers got in exchange for Mark Teixeira in 2007, struggled his first few years in the majors, posting a 5.39 ERA in 225 innings from 2008-2010. He had a breakout year in 2011, however, posting an ERA of 3.39 in 185.2 innings, and then followed that up with a 3.29 ERA in 213.1 innings in 2012, earning him a berth in the All Star Game.
Harrison, Derek Holland, and Yu Darvish are all now potentially under team control through the 2017 season.
UPDATE -- The 2018 option is a club option that vests based on innings pitched.
UPDATE II -- The salary breakdown is a $1M bonus, $5M in 2013, $8M in 2014, $13M from 2015-17, and a $13.25M club/vesting option for 2018 that could escalate to $15.75M, with a $2M buyout.