PHP：读取的字节数
假设我读取了这样的字节数：
$data = fread($fp, 4096);
由于 fread 如果到达文件末尾就会停止读取，我如何才能准确知道读取了多少字节？ strlen($data) 有效吗？或者这可能是错误的？
我想要完成的是读取多个字节，然后返回到读取之前的位置。我试图避免使用算术（ftell、fread、ftell、subract、fseek），因为文件可能大于 PHP_INT_MAX 并且可能会造成混乱。我想要的只是执行 fseek($fp, -$bytes_read, SEEK_CUR)，但为此我需要知道我刚刚读取了多少字节......
Say I read a number of bytes like this:
$data = fread($fp, 4096);
Since fread will stop reading if it reaches the end of the file, how can I know exactly how much was read? Would strlen($data) work? Or could that be potentially wrong?
What I'm trying to accomplish, is to read a number of bytes, and then go back to where I was before I read. And I'm trying to avoid using arithmetic (ftell, fread, ftell, subract, fseek), since a file could potentially be larger than PHP_INT_MAX and potentially mess that up. What I would want is to just do fseek($fp, -$bytes_read, SEEK_CUR), but for that I need to know how many bytes I just read...
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在
fread之后使用ftell($fp)< /a> 获取当前文件位置。After
freaduseftell($fp)to get the current file position.检查这一点（未经测试）：
第二个参数
'8bit'强制函数返回字节数。在 mb_strlen 的 php 手册 的评论中找到。
Check this (untested):
The second argument
'8bit'forces the function to return the number of bytes.Found in comments at php manual for mb_strlen.