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.
Nota: 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 install section if you experience this problem.