Say I read a number of bytes like this: $data = fread($fp, 4096); Since

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Asked: May 22, 20262026-05-22T19:24:27+00:00 2026-05-22T19:24:27+00:00

Say I read a number of bytes like this: $data = fread($fp, 4096); Since

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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…