nsapi_virtual() is an NSAPI-specific function which is equivalent to <!--#include virtual...--> in SSI (.shtml files). It does an NSAPI sub-request. It is useful for including CGI scripts or .shtml files, or anything else that you'd parse through webserver.
To run the sub-request, all buffers are terminated and flushed to the browser, pending headers are sent too.
You cannot make recursive requests with this function to other PHP scripts. If you want to include PHP scripts, use include() or require().
Note: This function depends on a undocumented feature of the Netscape/iPlanet/SunONE webservers. Use phpinfo() to determine if it is available. In the Unix environment it should always work, in windows it depends on the name of a ns-httpdXX.dll file. Read the note about subrequests in the NSAPI section (UNIX, Windows) if you experience this problem.