Libpq binary mode SELECT ... WHERE ID IN ($1) Question

Hello,

Suppose I have a table:
    create table foo ( id int4, name varchar(50) );

I want to prepare and execute in binary mode:
    select name from foo where id in ($1);

Execute works when I have a single value for $1, and treat it as a
normal INT4. However, when I attempt to send multiple values for the
parameter, I get no meaningful results.

My code snippets are below.

When setting up an array of numbers to pass as a parameter, is there
something special that needs to be done? The documentation is quite
vague; I did poke around the source and found in contrib some int_array
code, but don't fully understand it.

I suspect I need to do something like ...
(a) when I prepare, do something to tell postgres that I will have an
array of values, instead of a single value, and/or
(b) perhaps encapsulate the array of integers in some manner.

If I could be pointed to an example or documentation, it would be much
appreciated.

Thanks,
Matt Sanchez

The prepare code snippet:

Oid oids[1] = { 23 };   //INT4OID

result = PQprepare( pgconn, "getname",
"select name from foo where id in ($1)"
1, oids );

The execute code snippet:

int    ids[4] = { 3, 5, 6, 8 };    // param values we want to setup

/* convert numbers to network byte order ... */

char *    paramvalues[1] = (char *) ids;
int    paramlengths[1];
int    paramformats[1] = { 1 };

paramlengths[0] = = 4 * sizeof( int );

result = PQexecPrepared( pgconn,
    "getname",    // statement name
    1,        // number of params
    paramvalues,
    paramlenths,
    paramformats,
    1 );