Change (write) byte in file?

[alex101]

Is it possible to change a byte in a file using PHP without having to load the entire file into memory?

 

For example, if I just want to change the first or second byte in a file to 255 on a file which is extremely big (200GB) is it possible, without overloading the server?

 

There must be some kind of binary writing functions...

 

I'm asking this because I have a script that changes the first few bytes in files, but I've noticed that even though the number of bytes being changed is the same, the time it takes seems to depend on the size of the file, and not of the number of bytes being changed, making large files take extremely long to load, and then resulting in memory limit errors.