Globally install Composer on OS X 10.11 El Capitan

Update: this also works as expected with macOS Sierra.

The El Capitan release of OS X introduces a more strict security model around the concept of root level access to the underpinnings of the operating system. For a typical user, this is great news for avoiding malware, etc.

As a developer, this requires a little more thoughtfulness when trying to behave as root. Even with the sudo command, there are protected locations and processes that will no longer work as expected. To be specific /usr/bin for this example.

This command will NOT work in OS X 10.11:

curl -sS https://getcomposer.org/installer | sudo php -- --install-dir=/usr/bin --filename=composer

Yields an error, unable to write to the global path.

Downloading...
Could not create file /usr/bin/composer: fopen(/usr/bin/composer): failed to open stream: Operation not permitted
Download failed: fopen(/usr/bin/composer): failed to open stream: Operation not permitted
fwrite() expects parameter 1 to be resource, boolean given

Instead, let's write to the /usr/local/bin path for the user:

curl -sS https://getcomposer.org/installer | sudo php -- --install-dir=/usr/local/bin --filename=composer

Now we can access the composer command globally, just like before.