Interestingly, PHP uses separate operators for numerical addition (+) and string concatenation (.), so it's actually a bit more explicit than e.g. Javascript (where 'x + y' could result in normal numerical addition, or normal string concatenation, or implicit conversion to a numerical addition, or implicit conversion to a string concatenation!)
Only because Rasmus didn't know how to design and implement a "proper" programming language. This isn't a intended feature, it just made parsing easier for him.
The neat thing about PHP and the + operator is that you can sometimes trick the interpreter into doing math on the underlying bytes of the string: http://dominic-mulligan.co.uk/wp-content/uploads/2015/05/SRE...
Only to monopolize that operator to then have to use "->" for method call. C/C++ do that because of dereferencing. There is no need for that in PHP OO, all objects are passed by pointer to functions or methods.