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SitePoint PHP Blog:
Arbitrary Precision and Big Numbers in PHP
January 30, 2014 @ 10:20:46

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.

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PHP 10.0 Blog:
Making $$$ with PHP
April 02, 2007 @ 08:26:00

In a brieft post to the PHP 10.0 Blog today, Stas looks at a topic several PHPers out there have had to struggle with in their math-centric applications - how floats/doubles are handled in PHP.

Just wanted to write about the topic discussed elsewhere - how one could do money calculations with PHP? PHP has no BCD type and no arbitrary precision float type either. And for money calculations is it important to have it very precise - accountants can not allow even single penny to slip by (remember the plot of the Office Space movie?)

He basically says that the precision that PHP alone offers just isn't enough for some kinds of functionality. He also offers his own kind of solution proposal - switching the values back to (arbitrary-precision) integers and making all calculations in hundredth or thousandths of a cent.

Not that, according to Ron in the comments, there is in fact a BCMath extension already built for PHP.

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