What does it mean "to port over"

Solution 1:

"To port over" especially in the context of a computer system refers to moving functionality from one system or architecture to another. In your example:

where porting functionality over to the Zend Framework assumes that the system/program was probably written in php without the use of the zend framework and thus after rearchitecting/rewriting/moving the code to use the zend framework has resulted in better performance.

Solution 2:

From ODO:

port⁵verb
[with object and adverbial of direction]
1 Computing transfer (software) from one system or machine to another

Just as one can add over to verbs like carry and transfer to mean across some sort of divide, it can be used with port. The meaning is almost exactly identical.