Note that rewind($fd) is exactly the same as fseek($fd, 0, SEEK_SET)
rewind() just moves the location inside the file to the beginning, nothing more. Check if your stream is "seekable" before planning to use fseek/rewind.
(PHP 4, PHP 5, PHP 7, PHP 8)
rewind — 倒回文件指针的位置
将 stream 的文件位置指针设为文件流的开头。
注意:
如果将文件以附加（"a" 或者 "a+"）模式打开，无论文件指针位置如何，写入文件的任何数据总是会被附加在后面。
示例 #1 rewind() overwriting example
<?php
$handle = fopen('output.txt', 'r+');
fwrite($handle, 'Really long sentence.');
rewind($handle);
fwrite($handle, 'Foo');
rewind($handle);
echo fread($handle, filesize('output.txt'));
fclose($handle);
?>以上示例的输出类似于：
Foolly long sentence.
Note that rewind($fd) is exactly the same as fseek($fd, 0, SEEK_SET)
rewind() just moves the location inside the file to the beginning, nothing more. Check if your stream is "seekable" before planning to use fseek/rewind.