The package provides:

• StringHelper that has static methods allowing dealing with strings more efficiently;
• Inflector provides methods such as pluralize() or slug() that derive a new string based on the string given.

composer require yiisoft/strings

StringHelper methods are static so usage is like the following:

echo \Yiisoft\Strings\StringHelper::countWords('Strings are cool!'); // 3

Inflector usage is the following:

echo (new \Yiisoft\Strings\Inflector())->withoutIntl()->slug('Strings are cool!'); // strings-are-cool

Check both classes to find out about the methods available.