Replace mysql_connect() with new PDO(). Use prepared statements: $stmt = $pdo->prepare($sql); $stmt->execute([$param]); $row = $stmt->fetch(PDO::FETCH_ASSOC). The converter flags mysql_* with PDO pattern comments.
What new syntax does PHP 8 add?
PHP 8.0: named arguments, match expressions, nullsafe (?->), str_contains/str_starts_with/str_ends_with, union types, constructor promotion. PHP 8.1: enums, readonly properties. PHP 8.2: readonly classes.