The SitePoint PHP blog has a new post by Taylor Ren looks at big numbers in PHP and the functionality it has to handle arbitrary precision via three modules - GMP. BC Math and php-bignumbers.
In this article, we will review the PHP capability to provide arbitrary precision number calculation / big integer calculation by reviewing 3 PHP modules: GMP, BC Math and php-bignumbers. We will demonstrate two real-world examples to see the powers/limitations of each. The first one will be calculating PI to arbitrary precision - well, for the sake of the article, we will restrict the precision, say, to 1000 digits; the second will be a simple demonstration on RSA encryption/decryption.
He briefly looks at how to get the tools installed (via at-get or Composer) and a sample script to ensure that they're all included correctly and working. He includes a comparison between the three libraries, listing both strengths and weaknesses relative to the others. He then gets a bit more in-depth and shows how to calculate PI with each option (code is on GitHub) and the results of the benchmarking. He also includes a second example of calculating the RSA algorithm based on their process.