Set variable from php-code

[alex_svikk]

Good afternoon! Tell me, can I use the php-code to specify the value of this variable? That this variable, for example, was a value from the database. I assign $vboptions ['current_usd'] = '123'(current_usd - my variable name) to the usual static value for checking, but the variable is not displayed after saving. Help please.
Screenshot: (large)
https://i.imgur.com/8375Oa9.jpg