1. Registering a new PHP interpreter
A remote interpreter can be configured in a similar way as a local one. We can specify the PHP interpreter we want to use in Project Settings | PHP. This can be a local PHP installation or a remote PHP executable. Clicking ... next to the selected interpreter will open a list of registered PHP interpreters. Click the green + to add a new Remote....
When using a remote server, enter the SSH connection details to the host. Note that password authentication is supported, as is an OpenSSH or Putty key pair.
When using Vagrant support in PhpStorm, we can select the Vagrant option to automatically populate connection details. In most cases, PhpStorm can also figure out the path to the PHP interpreter on the Vagrant machine. If not, we can adjust it manually.
When one or more deployment configurations are present, for example when using Deployments in PhpStorm, the IDE will offer a third option: we can select the Deployment configuration option to use an existing configuration to connect to a remote PHP interpreter.
2. Selecting the remote PHP interpreter for the current PhpStorm project
Once a remote PHP interpreter is registered and configured, we can set up our project to use it during development. Simply select it in the dropdown list in Project Settings | PHP.
Once configured, all our Run/Debug configurations will make use of the configured PHP interpreter. Since we just configured a remote PHP interpreter as the one that should be used for our project, the following run configuration will always run on the remote server or Vagrant machine.
3. Using the remote PHP interpreter
Once configured, we can start using our remote PHP interpreter, for example for unit testing. Check the tutorial Running PHPUnit tests over SSH on a remote server with PhpStorm for more information.
(optional) Composer and Remote PHP Interpreters
PHP interpreter is a project setting in PhpStorm: it will be used for all actions that require the PHP executable, for example for running the various Composer commands. When a remote PHP interpreter is configured, the Composer Support in PhpStorm may break because the remote PHP interpreter will potentially not have access to the project path on our development machine.
Through Project Settings | PHP | Composer, we can specify the PHP interpreter to use for running Composer commands.
Once configured, PhpStorm will use the remote PHP interpreter for commands that can be run remote, for example running PHPUnit tests, and a local interpreter for Composer.