Doubt about a Challenge

Question

Just had a challenge in PHP.
This is the question

Guess the output.
$x=5;
echo("$x");

Answer:5.

Should not the answer be $x?

Answer 1

Variables in double quote strings are evaluated.

https://stackoverflow.com/questions/3446216/what-is-the-difference-between-single-quoted-and-double-quoted-strings-in-php

Answer 2

Thnx.