Get Request Query Value as a string (Laravel/Php)

Hello, i'm working on vue + laravel, from vue i'm making get request (with query parameter) to laravel, as result i get something like feed?search=#somestring, so, in laravel i want to get this query parameter, but as a string, i can get it like request('search') and check if it exists or something, but cannot check for the string inside.. i want to check if string in query parameter starts with certain letter. so, how can i check if query start with a certain letter, or get certain query-s value? (btw i have multiple query-s for this route, so i also need to get certain query-s value(as a string, to then check it by php helper methods ), not for all of them) Thank you.