<p>I have a website cgi-bin program that is written in c++. </p>

<p>Unfortunately the website provider for my friend's site only allows Perl or PHP cgi-bin scripts.</p>

<p>Is there an easy way to simply have a very small Perl or PHP wrapper that just calls the c++ compiled binary? </p>

<p>Would the c++ program still be able to read from stdin for POST commands or would it have to be read by the Perl or PHP and then forwarded.</p>

You can use PHP's system() function to execute a shell command, which you could use to launch another program.  The STDOUT of that program would then go to the same place as php's stdout (to the HTTP connection).  You might have to do some messing around to get stdin to read from get/post/etc.
But most likely the website provider has disabled the ability of you to execute programs in this way.  It can be a security risk, and if they specifically only allow php and perl, then they would probably specifically disable as many methods of running non-php/perl as they could. So, short answer is you're probably out of luck.