Sony's Cameron Diaz starrer Sex Tape opened to just $5.7 million on Thursday, tracking towards a $16 million overall weekend. The comedy, which cost $40 million, suffered frightfully bad reviews and scored just 19% on reviews aggregating website Rotten Tomatoes.

Sex TapeCameron Diaz [L] and Jason Segel [R] in 'Sex Tape'

Elsewhere, the top movie on opening night was horror The Purge: Anarchy, which earned a solid $13 million. The original movie opened last June to a $16 million Friday and went on to gross $34 million on its opening weekend. Anarchy should gross around $27 million by the end of the weekend, three times its production budget.  

The Walt Disney animation Planes: Fire and Rescue - which is better than the original - took $6.29 million on opening day and should earn around $17.6 million for the weekend. That figure is noticeably less than the $22 million earned by the original, though it should easily recoup its $50 million budget in DVD and BluRay sales anyway.

Finally, Dawn of the Planet of the Apes earned $10.4 million on its second Friday and should earn $31 million for its second weekend - enough to top the box office again unless The Purge: Anarchy pushes on. The movie has now passed the $100 million mark in the U.S and has now grossed over $271 million worldwide.

Next week sees the release of Dwayne Johnson's 'Hercules', and sci-fi Earth to Echo.