php使用生成器读取超大文件

<?php

function getLines($file) {
    $f = fopen($file, 'r');
    try {
        while ($line = fgets($f)) {
            yield $line;
        }
    } finally {
        fclose($f);
    }
}

foreach (getLines("logs.log") as $n => $line) {
    //逐行内容
    echo $line;
    //行数
    var_dump($n);
}