When must arbitrary precision arithmetic functions be used in PHP?
<p>My colleague uses the <a href="http://www.php.net/manual/en/ref.bc.php" rel="nofollow">Binary Calculator functions</a> in bandwidth calculations; as much as terrabytes, and with percentage splitting on allocation. His usage of these functions appears correct in order not to lose a byte; although he seems to be using them now for everything.</p>

<p>The manual only says: </p>

<blockquote>
  <p>For arbitrary precision mathematics PHP offers the Binary Calculator which supports numbers of any size and precision, represented as strings. </p>
</blockquote>

<p>How much is any size? Is it really necessary? How big is the default float in PHP? Are there any good advice regarding this or things to keep in mind?</p>
