Good all the time of day.
This is how I cannot understand PHP programming in the context of mathematics + logic, addition and connection.
An example is here .
Explain how it works and why?

    1 answer 1

    This is the basics. Unlike Delphi, in PCP there is an addition operator, and there is a string concatenation operator.

    So here. If the addition operator (plus) is used, it converts its arguments to numbers, and then adds. The concatenation operator (dot) does this with strings. If the argument is a number, it converts it first to a string.

    Since the conversion string-> number is not always possible, it turns out a variety of artifacts.

    If from the given examples in the picture, some specific thing is incomprehensible, copy it here, let's look at it.

    ps never again give php text a picture!