Description:
------------
When trying to insert an empty string into a varchar field, the field is filled with blanks, i.e. the length isn't set to zero. This happens regardless of allowing null for this field or not.

Reproduce code:
---------------
Assuming there's the table 'blank_tbl' in library 'blank' containing of a single varchar field with maximum length 10.
A          R PHPS
A            BLANK_FLD     10          VARLEN

<?php
$dbname = '*';
$username = '*';
$password = '*';

if (($database = db2_connect($dbname, $username, $password)) === false) die(db2_conn_errormsg());

$sql = <<<EOT
INSERT INTO blank.blank_tbl(blank_fld)
VALUES (?)
EOT;

$data = array('');

if (($stmt = db2_prepare($database, $sql)) === false) print_r(db2_stmt_errormsg());

if ($stmt && db2_execute($stmt, $data) === false) print_r(db2_stmt_errormsg($stmt));

db2_close($database);
?>

Expected result:
----------------
A row should be inserted into the table, with the single field beeing an empty string.

Actual result:
--------------
The row is inserted, but the string consists of blanks, filled up to the maximum length.

Taking a look at the data directly (aka PDM) shows these hex contents:
004444444444
0A0000000000