Sporting Lisbon have accepted Joel Campbell's 'challenge' and signed the Arsenal forward on a season-long loan deal.
The Costa Rica international made 19 Premier League appearances for Arsene Wenger's side last season but has moved away from the Emirates Stadium in search of regular game time.
Sporting announced the signing in bizarre fashion on Twitter as Campbell tweeted the club's official account urging them to secure his services, which prompted the club to confirm his rival a minute later.
An Arsenal club statement said: "Everyone at Arsenal wishes Joel a successful season in Portugal.
"The move is subject to international clearance and formal ratification."
Campbell joined Arsenal in 2011 and has had spells on loan at Lorient, Real Betis, Olympiacos and Villarreal in an effort to force his way into Wenger's plans but remains behind the likes of Theo Walcott and Alex Oxlade-Chamberlain in the pecking order.
Arsenal's central defender transfer shortlist
Campbell's move is the second time an Arsenal transfer has involved a unique social media exchange this summer.
Rob Holding, who is one of three players to join Arsenal this summer, was announced by the Gunners during a quiz when the club tweeted a photograph of the back of his head
