What does PHP GMP Extension do?

@thebigk - The description of php-gmp shows

Name        : php-gmp
Arch        : x86_64
Version     : 7.2.11
Summary     : A module for PHP applications for using the GNU MP library

Description : These functions allow you to work with arbitrary-length integers using the GNU MP library.

The GNU MP Library has documentation here

There are examples available on the PHP website

http://php.net/manual/en/gmp.examples.php

Essentially the difference is regular integers are constrained in length, wheras GMP allows integers and integer maths with any length

The size of an integer is platform-dependent, although a maximum value of about two billion is the usual value (that's 32 bits signed). 64-bit platforms usually have a maximum value of about 9E18, except on Windows prior to PHP 7, where it was always 32 bit.

Thanks. What'd be the practical application of this?

@thebigk - You can use the gmp functions to do maths on numbers larger than can be stored in a regular integer.

@thebigk, practical applications abound, and some are listed here:

https://en.wikipedia.org/wiki/GNU_Multiple_Precision_Arithmetic_Library

But even for mundane programming MP libraries can support more flexible or careless (if you will) coding of mathematical operations. A common problem I've encountered is say abcd/e/f/g forms, where the produce all elements are simple ints or floats or doubles say, and the result is also easily represented in ordinary data data types but intermediate product abcd causes an arithmetic overflow.

That's a trivial example as it's easy to rearrange to a/eb/fc/g*d and avoid an overflow typically (which is why I say careless coding, but there are many more complex algorithms that run into the problem of needing or benefiting from more intermediate precision than standard data types and operators support.

But if you've never encountered, or felt a desire or need to store a number that exceeds the capabilities of standard data types then don't worry about it. It's not for you ...