Writing to process STDIN and reading its STDOUT from PHP4?

Can someone explain how I can send STDIN to a *process* and read its STDOUT from PHP4? The only function I could find in the manual that seemed relevant was popen(), but the manual says that it is unidirectional only. There must be a better way than than writing to a temp file and calling the process via popen("process < tmpfile", "r") ... I hope ? Anyone willing to provide a simple example of the best way to do this? Suppose, for example, I have a paragraph of text contained in variable $text, and I want to pass this to the STDIN of a binary called 'program' and read its STDOUT back into PHP4. Thanks in advance!