array_push() vs. $array[] = .... Which is fastest?

It depends...

Documentation says,

"If you use array_push() to add one element to the array it's better to use $array[] = because in that way there is no overhead of calling a function."

Source: http://us2.php.net/array_push

So it boils down to how much data you want to cram into that array at any particular moment.

Additionally, there's a fall-back. If the array-referenced doesn't exist when you call it using array_push, you'll bump an error. If you use $array[], the array will be created for you.

You can run it and see that array_push is slower in some cases:

http://snipplr.com/view/759/speed-test-arraypush-vs-array/

Run your code. Enjoy.