Function to_writer 

pub fn to_writer<W: Write, T: Serialize + ?Sized>(
    writer: W,
    value: &T,
) -> Result<(), Error>

Serializes a value to a writer.

let mut out = Vec::new();
deser_php::to_writer(&mut out, &vec!["a", "b"]).unwrap();
assert_eq!(out, br#"a:2:{i:0;s:1:"a";i:1;s:1:"b";}"#);