Symfony polyfill for the Mbstring extension

 This component provides a partial, native PHP implementation for the
 Mbstring extension.
 .
 The Symfony Polyfill project backports features found in the latest PHP
 versions and provides compatibility layers for some extensions and functions.
 It is intended to be used when portability across PHP versions and extensions
 is desired.
 .
 Symfony is a PHP framework, a set of tools and a development methodology.