ODBC Prepared Statement Issues

I am trying to execute multiple prepared statements in PHP via the ODBC
functions. The first execution succeeds, but any proceeding executions
throws a recoverable error. This does not occur with the standard or PDO
extensions. Only Oracle has a similar issue. I tried using the standard
$1,$2,etc., binding markers and it threw a totally different error.

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Here is the PHP code:

$dbh = odbc_connect('Driver={PostgreSQL
Unicode};Trusted_Connection=yes;Server=localhost;Port=;Database=test_pgsql;','postgres','pass',SQL_CUR_USE_ODBC
);

$rs = odbc_prepare( $dbh, 'insert into rock_star (f_name,l_name)
values(?,?)' );

odbc_execute( $rs, array( 'Brian', 'Jones' ) );
echo 'Inserted 1: ' . odbc_num_rows( $rs );

odbc_execute( $rs, array( 'Rory', 'Gallagher' ) );
echo 'Inserted 2: ' . odbc_num_rows( $rs );

odbc_close( $dbh );

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Expected Results:

Inserted 1: 1
Inserted 2: 1

Actual Results:

Inserted 1: 1

Warning: odbc_execute(): SQL error: Unfortunatley couldn't get this
paramater's info, SQL state S1000 in SQLDescribeParameter in
G:\www\dev\Projects\test_odbc.php on line 26

Inserted 2: 1

Although the "Inserted 2" output returns 1, the insert is never executed.
The odbc_prepare() method does not require odbc_free_result() between
executions.

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Environment:

Windows NT BUZZ 6.1 build 7601 (Windows 7 Home Premium Edition Service Pack
1) i586
Apache/2.4.2 (Win32) PHP/5.5.9
PostgreSQL 9.3 (x86)
PostgreSQL Unicode 9.03.01.00