PHP is usually easier to scale because it just a matter of how many webservers. e.g. apache or nginx, you choose to deploy.
This also possible with other platforms, but can be a bit trickier to get right.
For large PHP setups it is usually the number of database connections that is the limiting factor, however that is why historically the replicated MySQL databases was such a good fit for PHP, thus only creating a limit for writes on the master.
