The Associated Press, citing a source, said an NBA trade call was needed to complete the deal prior to the 3 p.m. ET trade deadline.
Philadelphia will become the sixth club for the well-traveled Ennis, who averaged 7.4 points for the Rockets this season.
Ennis has also played for Miami, New Orleans, Memphis and Detroit. He's a career 36 percent shooter from 3-point range and will add to Philadelphia's bench depth.
The Rockets, who will create a $1.6 million trade exception with the deal, are inching their way closer to getting under the luxury tax. The Rockets save $2.4 million with the trade and are now $2.4 million above the tax threshold.
Houston started the season with a tax bill of $14.6 million.
ESPN's Bobby Marks and The Associated Press contributed to this report.