PHP读取错误的数据

Question

I'm reading a binary file in PHP:

$File = fopen('simplefile', 'rb');
// Random stuff
fseek($File, $APosition);
for($I = 0; $I < 10; $I ++ ){
    var_dump(unpack('V', fread($File, 4)));
}
fclose($File);

However this does not give correct output for that position (it is giving 6357101 not 4294967295 as expected - I've checked using a hex editor).

However, this work and gives the correct values:

$File = fopen('simplefile', 'rb');
// Random stuff
fseek($File, $APosition);
for($I = 0; $I < 10; $I ++ ){
    fseek($File, ftell($File));  // What is this line doing?
    var_dump(unpack('V', fread($File, 4)));
}
fclose($File);

This however, I don't understand as surely fseek($File, ftell($File)); does absolutely nothing? What is that line doing and how can I read the correct values without errors?

---

This segment of the file is just 0xFF repeated several hundred times.

Answer 1

I set up a file of all FF bytes, and the loop correctly reads -1 ten times, which is 4294967295 unsigned. I can't reproduce the value you get.

The value you are getting, 6357101, corresponds to the bytes 6D 00 61 00. That is the characters 'ma' encoded in UTF-16, although it could also mean other things.

I think the file or the content of the file is not what you think it is, or you are reading from the wrong place.

fseek($File, ftell($File));  // What is this line doing?

It should do nothing. If it doesn't do nothing I can only speculate that perhaps the file is corrupt on disk, or your copy of PHP is borked, or your computer has gone quietly mad.