How Can I Get Multiple Drop Down List Using Php That Should Look Like If I Select One Item Then It Must Open Other Set Of Options In Other Dropdown

Whether you are using any database (like mysql or postgres) or not in your project?
If yes, then it will be easy to do this.
Take one table for second dropdown in database, store three columns in database, one column will store value of select option and other column will store text of select option and third column will store value of first dropdown. If you select any text from first dropdown, then second dropdown will be populated with entries where third column value match with the value of first dropdown selected.