PHP 7.2 upgrade advises to "use curly braces to remove ambiguity"

I am updating my WordPress site from PHP 5.5 to PHP 7.2.

PHP compatibility checker has advised the following for header & footer:

27 & 30 | ERROR | Indirect access to variables, properties and methods will be evaluated strictly in left-to-right order since PHP 7.0. Use curly braces to remove ambiguity.

Line 24-33 reads:

---extract from Header.php---

global $options;
foreach ($options as $value) {
    if (isset($value['id']) && get_option( $value['id'] ) === FALSE && isset($value['std'])) {
        $$value['id'] = $value['std'];
    }
elseif (isset($value['id'])) {
    $$value['id'] = get_option( $value['id'] );
    }
}
?>

---extract from Header.php---

Line 27 reads as:

$$value['id'] = $value['std'];**

Line 30 reads as:

$$value['id'] = get_option( $value['id'] );

How should I use curly braces to fix the two statements above?

It's the dynamic variable name $$value['id'].

On previous/older PHP versions it was fine to declare it like that but starting PHP 7.0 you need to use curly braces to make it more readable/evident and avoid confusion:

${$value['id']} = $value['std'];

${$value['id']} = get_option( $value['id'] );

See PHP - Variable variables for more details.