(PHP 7 >= 7.4.0)
FFI::memcpy — Copies one memory area to another
&$dst
   , mixed  &$src
   , int $size
   ) : void
   Copies size bytes from the memory area src
   to the memory area dst. Both src and
   dst can be any native data structures (FFI\CData)
   or PHP strings.
  
dstThe start of the memory area to copy to.
srcThe start of the memory area to copy from.
sizeThe number of bytes to copy.
No value is returned.