yield

<?php

function ff($e){

    for($i=0;$i<$e;++$i){
    yield $i;
    }
}

$iter=ff(11);
foreach($iter as $v)..

while($iter->valid()){
echo $iter->current();
$iter->next();
}
...
function logger($fileName) {
    $fileHandle = fopen($fileName, 'a');
    while (true) {
        fwrite($fileHandle, yield . "\n");
    }
}

$logger = logger(__DIR__ . '/log');
$logger->send('Foo');
$logger->send('Bar');

function html($fileName='php://output'){

    $h = fopen($fileName, 'w');

     try {
    fwrite($h,'@start');


    fwrite($h, (yield 'ok'));
    fwrite($h,'@end');

    } finally {
        fclose($h);
    }


}

$i=html( );

$msg=$i->current();
$i->send($msg.':'. 123);