integer division in php

Question

I'm looking for the fastest way to do an integer division in php. for example, 5 / 2 should be 2 and 6 / 2 should be 3 and so on. If I simply do this, php will return 2.5 in the first case, the only solution I could find was using intval($my_number/2) - which isn't as fast as I want it to be (but gives the expected results).

How can I do this?

EDIT:
Thanks to all of you for your ideas, I used the script posted by rubber_boots to test some of them with 10000000 iterations, here you can see the results (MAMP on a 3 or 4 year old MacBook with 2Ghz Intel core 2 duo):

start (10000000) (int)...: 2.26 sec floor(): 4.36 sec int_divide(): 2.86 sec bit-shift: 1.45 sec //note: only works for divisions through powers of 2 intval(): 4.51 sec round() with PHP_ROUND_HALF_DOWN: 5.48 sec 

until now, bit-shift is the fastest way, but I'll leave this question open for a day to see if there are other possibilities for this...

EDIT2:
updated the results, added round() with PHP_ROUND_HALF_DOWN (thanks to Col._Shrapnel)

Answer 1

Just cast it to an int:

$result = (int)(6 / 2); 

For whatever reason, it's much faster than intval().

Edit: I assume you are looking for a general integer division solution. Bit-shifting is a special case for dividing by (or multiplying by) powers of 2. If that interests you then:

a / b^n = a >> n where a, b, n are integers 

so:

a / 2 = a / 2^1 = a >> 1 

But two caveats:

1. Many compilers/interpreters will do this for you automatically so there is no point second guessing it;

2. Unless you're doing this division at least 100,000 times in a single script execution don't bother. It's a pointless micro-optimization.

To further elaborate on (2), yes (int) is faster than parseInt() but does it matter? Almost certainly not. Focus on readable code and a good algorithm. This sort of thing is an irrelevant distraction.

Answer 2

if it's division by 2, the fastest way to do it is bit shifting.

5>>1 = 2 6>>1 = 3 

and so on and so forth. What it does is just shift the bits to the right by 1 bit, thus dividing the number by 2 and losing the rest

1110 >> 1 =  111 1011 >> 1 =  101 1011 >> 2 =   10 //division by 4 1011 << 1 =10110