How to solve the problem with special characters on PhantomJS+MTS PHP?

Question

PHP

I am using phantomJS+MTS PHP to fill out forms, here is a piece of code:

$windowObj->mouseEventOnElement("[id=address-enterAddressLine1]","leftclick");
    $windowObj->sendKeyPresses($address_street1);

Everything works well, if special characters, for example, umlauts, do not appear in $address_street1, then an error appears.
If you make htmlentities, then the word is entered into the form, but ö will be - ö
Tell me how to fix this situation?