(PHP 8 >= 8.1.0)
fdatasync — Synchronizes data (but not meta-data) to the file
$stream): bool
This function synchronizes stream contents to storage media, just like fsync() does,
but it does not synchronize file meta-data.
Note that this function is only effectively different in POSIX systems.
In Windows, this function is aliased to fsync().
成功时返回 true， 或者在失败时返回 false。
示例 #1 fdatasync() example
<?php
$file = 'test.txt';
$stream = fopen($file, 'w');
fwrite($stream, 'test data');
fwrite($stream, "\r\n");
fwrite($stream, 'additional data');
fdatasync($stream);
fclose($stream);
?>