Empty string bound to `NVARCHAR` fails

[NattyNarwhal]

Found from a user report. Reproduces on IBM i:

<?php
  
$c = db2_connect("*LOCAL", "", "") or die("can't connect\n");

db2_exec($c, "CREATE OR REPLACE TABLE QTEMP.AH_REPRO(FLSFNUM NVARCHAR(2048))") or die("can't make table\n");

$parm = "";

$s = db2_prepare($c, "INSERT INTO QTEMP.AH_REPRO VALUES(?)");
db2_bind_param($s, 1, "parm", DB2_PARAM_IN);

db2_execute($s) or die("can't execute insert\n");

$s = db2_prepare($c, "SELECT * FROM QTEMP.AH_REPRO");
db2_execute($s) or die("can't execute select\n");

while (($r = db2_fetch_assoc($s)) != false) {
        var_dump($r);
}

Fails with:

Warning: db2_execute(): Statement Execute Failed in /home/CALVIN/ah.php on line 12

Warning: db2_execute(): Mixed data or UTF-8 data not properly formed. SQLCODE=-191 in /home/CALVIN/ah.php on line 12

Changing $parm to a non-empty string or the column to plain VARCHAR works correctly. Looks like the only difference when called is SQLBindParam's fSqlType type has SQL_WVARCHAR instead of SQL_VARCHAR.

[NattyNarwhal]

I think the problem is we're missing the other data types for the SQL_NTS bit just before calling SQLBindParameter. This diff seems to fix it for me, at least for the SQL_WVARCHAR case (others untested):

diff --git a/ibm_db2.c b/ibm_db2.c
index 6a4149e..e26b780 100644
--- a/ibm_db2.c
+++ b/ibm_db2.c
@@ -4578,6 +4578,11 @@ static int _php_db2_bind_data( stmt_handle *stmt_res, param_node *curr, zval **b
                     paramValuePtr = (SQLPOINTER)(Z_STRVAL_P(curr->value));
                     break;
                 case SQL_VARCHAR:
+                case SQL_WVARCHAR:
+                case SQL_VARGRAPHIC:
+                case SQL_LONGVARCHAR:
+                case SQL_WLONGVARCHAR:
+                case SQL_LONGVARGRAPHIC:
                     valueType = SQL_C_CHAR;
                     if (origlen != -1) {
                         curr->bind_indicator = origlen;

[kadler]

Yeah, IBM i CLI has a peculiarity that you can't bind an empty string unless you pass it as SQL_NTS 🙃