On local server when we make changes in php.ini file server restart is required. But on shared hosting like hosting on DreamHost making changes in php.ini file should work. Generally shared hosting provides php.ini file, you can add always_populate_raw_post_data = -1 in a new line and that should work.
Let me know if this helps.
Note: On VPS server you can simply restart apache server.
Note: Restart server means restarted httpd services (Avoiding confusion over here)