mysql database question. what are the alternatives for mysql_query() and mysql_result() functions as i found out that they were deprecated in php7.

in other words i have this function how can i properly change mentioned mysql functions to the new ones?

function user_exists($username) {

$username = sanitize($username);

$query = mysql_query("SELECT COUNT('id') FROM 'users' WHERE 'username' = '$username'");

return (mysql_result($query, 0) == 1) ? true : false;

}