Como chamar o procedimento armazenado usando PHP e SQL Server 2008

$conn = mssql_connect($host, $user, $pass);
mssql_select_db('somedb', $conn);

// Call a simple query
$result = mssql_query('SELECT * FROM sometable', $conn);

// Release the result resource
mssql_free_result($result);

// Then execute the procedure
$proc = mssql_init('some_proc', $conn);
$proc_result = mssql_execute($proc);

// Etc...
mssql_free_statement($proc);

$conn = odbc_connect("Driver={SQL Server Native Client 10.0};Server=$server;Database=$database;", $user, $password);
$exec = odbc_exec($conn, "CALL storedProc()");

$a = 1;
$b = 2;
$c = 3;
$stmt    = odbc_prepare($conn, 'CALL myproc(?,?,?)');
$success = odbc_execute($stmt, array($a, $b, $c));