If PHP's mt_rand() uses a faster algorithm than rand(), why not just change rand() to use the newer implementation?
<p>The purpose of a random number function is to get -- you guessed it -- a random number, something you cannot predict (or be very hard to predict with certainty). If the <code>mt_rand()</code> function is faster and less predictable (more "random") than the old <code>rand()</code>, why not just switch the underlying implementation to the new method? </p>

<p>To put it another way, what kind of program that uses <code>rand()</code> would break in a later version of PHP if/because the underlying implementation changed?</p>
