Is the question "The new iPhone is out?" valid english? [duplicate]

My friend asked me over text:

"The new iPhone is out?"

Is this valid English? I say it's not, but he believes it is. I believe the correct question would have been:

"Is the new iPhone out?"

The grammar just seems backwards to me, is it correct English?

The sentence is grammatical both ways. There is a subject and a verb.

Inversion of subject and auxiliary verb is a common way of forming questions in English. But, verbal inflection is also a manner of forming questions. (Have you ever asked someone the [fragmented] question, "Beer?")

Consider the following:

He did run out the door?

This is still a question, even though the subject is before the verb. If this were spoken, it would likely require the verbal inflection at the end of the word to signify it being a question.

Most often, this would be a question of confirmation. But that doesn't make it less grammatical.

Arguably, it would have been clearer to ask:

Did he run out the door?

The order of the subject and verb is merely a matter of style at this point.