Python works:
>>> sum(x for x in xrange(1000000000 + 1))
500000000500000000
Or:
>>> sum(xrange(1000000000+1))
500000000500000000
Python’s int auto promotes to a Python long which supports arbitrary precision. It will produce the correct answer on 32 or 64 bit platforms.
This can be seen by raising 2 to a power far greater than the bit width of the platform:
>>> 2**99
633825300114114700748351602688L
You can demonstrate (with Python) that the erroneous values you are getting in PHP is because PHP is promoting to a float when the values are greater than 2**32-1:
>>> int(sum(float(x) for x in xrange(1000000000+1)))
500000000067108992