Significant digits

[mojsoskid]

I am using the library for matrix multiplication and system of linear equations. I am using php 7.1 with Debian. I have read the docs before but I couldn't find any information on the maximum number of significant digits. I know that in PHP this can be modified using php.ini but some of the results I got when using calculations with the functions of NumPHP had 20+ significant digits. I would like to know what is the maximum number and if there is a way to set a fixed number of significant digits for all computations. Thanks in advance.