Mixing a PHP variable with a string literal

echo “{$test}y”;

You can use braces to remove ambiguity when interpolating variables directly in strings.
Also, this doesn’t work with single quotes. So:
echo ‘{$test}y’;

will output
{$test}y

You can use {} arround your variable, to separate it from what’s after:
echo “{$test}y”

As reference, you can take a look to the Variable parsing – Complex (curly) syntax section of the PHP manual.