No, the OOP style isn't better. The set of functions one can use in OOP is closed.

Imagine I want to AfD a custom string function for a feature which uPpErCaSeS every second letter as I need that for some purpose: I can't do in OOP style.

In OOP I could extend the string class, but most other parts of the code won't magically use my string type now.

Thus I have to create a free standing function for this (which probably also is better as I don't need internal state of thee object, thus livingnoutisde is good for encapsulation)

And thus my string function works different from other string functions.

    my_casing($string->trim())->substr(3);

Having them all be simple functions makes it equal.

Of course there are alternative approaches. C++ argues for years about "uniform call syntax" which would always allow "object style" function calls, which could also find non-memwbr functions where the first argument is of compatible type, but such a thing requires stricter (or even static) typing, this won't work in PHP.