Description:
------------
Calling odbc_execute modifies the input paramList array.
This happens even when I try to make a copy of the array before passing it to odbc_execute.

Specifically, null parameters are changed to zero length strings.


Reproduce code:
---------------
<?php
    function x( $query, $paramList )
    {
        $result = odbc_execute( $query, $paramList );
	    $paramList['timg'] = "Tim Gallagher";
    }

    // change the server and database below to the correct values for your setup
    $connection = 'DRIVER={SQL Server};SERVER=server;DATABASE=database';

    $handle = odbc_connect( $connection, '', '' );
    $query  = odbc_prepare( $handle, "INSERT INTO TEST (ID,CHECK_LONG,CHECK_VARCHAR) VALUES (?, ?, ? )" );

    $paramList[0] = 44;
    $paramList[1] = null;
    $paramList[2] = null;

    echo gettype($paramList[2]) . "\n"; // echos NULL
    x( $query, $paramList );
    echo gettype($paramList[2]) . "\n"; // echos string
    
    print_r( $paramList )

?>

Expected result:
----------------
NULL
string
Array
(
    [0] => 44
    [1] => 
    [2] => 
)

Actual result:
--------------
NULL
NULL
Array
(
    [0] => 44
    [1] => 
    [2] => 
)