<?php function doStuff() { $generatorCallback = function ($buffer) { yield yield; }; ob_start(function ($buffer, $phase) use ($generatorCallback) { $generatorCallback->send($buffer); }); print "foo"; print "bar"; ob_end_clean(); foreach ($generatorCallback as $bufferLine) { yield $bufferLine; } } foreach (doStuff() as $foo) { var_dump($foo); }