generator-testcase.php

<?php
date_default_timezone_set("America/New_York");
function gen() {
    $i = 0;
    while (true) {
        file_put_contents("./log", 
            date("Y-m-d H:i:s") .' '.
            (yield $i++) . ' ' .
            PHP_EOL
        , FILE_APPEND);
    }
}

$gen = gen();
var_dump($gen->send("First Call")); // 1
sleep(3);
var_dump($gen->send("Second Call")); // 2

log

2013-02-04 02:35:46 First Call 
2013-02-04 02:35:46 Second Call