gistfile1.php

<?php
class StreamThingy {
	public $fh; //this si your fopen statement
	public $readFunc;
	
	public function onRead($function) {
		$this->readFunc = $function;
	}
	
	public function execute() {
		$this->fh = //do fopen logic
			$bytes = 4096;
			while($str = call_user_func(array($this, 'readFunc'), $fh, $bytes) !== FALSE) {
				//do something here
			}
	}
}

$streamObj = new StreamThingy();

$streamObj->onRead(function($handle, $bytes) { return fread($fh, $bytes); });

$streamObj->execute();