Binary-safe file write
fwrite ( resource $handle , string $string [, int $length ] ) : int
A file system pointer resource that is typically created using fopen().
The string that is to be written.
If the length argument is given, writing will stop after length bytes have been written or the end of string is reached, whichever comes first.
Note that if the length argument is given, then the magic_quotes_runtime configuration option will be ignored and no slashes will be stripped from string.
Returns the number of bytes written, or FALSE on error.