It's not a fluke. It's also not called a prefix, but an 'argument' to the 'php' command.
On your Linux machine, run "man php" and you find all the arguments that you can use for PHP. If you don't have a Linux machine, then Google it and you'll find the online version of the PHP Man page.
The '-f' argument that they have added tells PHP to "parse and execute the following file" and then they give it the file. That's why it suddenly works. Some PHP installations, depending on version and security rules, require the -f and others done (such as mine).
As for the sendmail fix, my ISP requires that the sendmail path in my PHP.ini file look like this:
sendmail_path = /usr/sbin/sendmail -t -i;
The -t and -i arguments have to be there in order for PHP to be able to send out emails. Make sure that the sendmail path on your installation is setup correctly.