PHP round to integer

I want to round a number and I need a proper integer because I want to use it as an array key. The first “solution” that comes to mind is:

$key = (int)round($number)

However, I am unsure if this will always work. As far as I know (int) just truncates any decimals and since round($number) returns a float with theoretically limited precision, is it possible that round($number) returns something like 7.999999… and then $key is 7 instead of 8?

If this problem actually exists (I don’t know how to test for it), how can it be solved? Maybe:

$key = (int)(round($number) + 0.0000000000000000001) // number of zeros chosen arbitrarily

Is there a better solution than this?

Answer

To round floats properly, you can use:

• ceil($number): round up
• round($number, 0): round to the nearest integer
• floor($number): round down

Those functions return float, but from Niet the Dark Absol comment: “Integers stored within floats are always accurate, up to around 2^51, which is much more than can be stored in an int anyway.”