I found a typo in the following page:  http://developers.marketo.com/documentation/soap/getmultipleleads/
The Request reference section lists out the "streamPosition" field for pagination.  However the PHP sample code displays the  the following:
- 
		$params->startPosition = $startPosition;
 
	This code line does nothing in the example for 2 reasons:
	
		1) $startPosition is never set and that's ok for the initial call to getMultipleLeads 2)startPoistion is the wrong name.
	The code should be as the following:
- 
			$params->streamPosition = $startPosition;