Can PHP code access (as a string) the accumulating output stream?

Hello, PHP gurus. This is a long shot. I am wanting to know if there is a method available from within PHP code, by which I can fetch (in a string) the current contents of the HTML output stream. The ideal and simplest implementation of this idea would be a hypothetical system function getOutput(), which would return the current serialised output as a string. The statement : $strOutput = getOutput(); would return whatever was in the output buffer at the time. This would be a very powerful facility if available. I have a particular application in mind where I want to use it. I would be very grateful if anyone could answer my question. Cheers! Mark Moorhouse