Writing into buffers in PHP -

I come from the node. Js and I just do some work with it:

  buf .writeUInt16LE (data, offset);  

Now I need something similar in PHP. I currently have:

  protected $ tmpl = '06007007010001004B4'; $ Byte = Unpack ('C *', $ this-> TMPL);  

But does the offset for the pack function argument do not seem to be any option?