Description:
------------
pdo_oci does not convert oracle nulls to php nulls when fetching from lob fields. Appears in 5.0.5 to 5.1.2 versions of php/pdo/pdo_oci. Oracle version is 10g. Non-lob fields appear to convert just fine.

Setting the PDO::ATTR_ORACLE_NULLS driver attribute to PDO::NULL_TO_STRING and/or PDO::NULL_EMPTY_STRING has no effect.

I'm aware that this behaviour is 'by design' for oracle but was led to believe by the docs that pdo handled nulls for me so I don't have to resort to using NVL(...) in my queries.

Reproduce code:
---------------
<?php

error_reporting(E_ALL);
$dbh = new PDO('oci:', 'scott', 'tiger');
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);

var_dump($dbh->query("SELECT * FROM SCOTT.EMP")->fetch(PDO::FETCH_ASSOC));

if($dbh->exec("ALTER TABLE SCOTT.EMP ADD (PIC BLOB)") === false) {
  die("ALTER TABLE failed.");
}

var_dump($dbh->query("SELECT * FROM SCOTT.EMP")->fetch(PDO::FETCH_ASSOC));

$dbh->exec("ALTER TABLE SCOTT.EMP DROP (PIC)");

?>

Expected result:
----------------
array(8) {
  ["EMPNO"]=>
  string(4) "7369"
  ["ENAME"]=>
  string(5) "SMITH"
  ["JOB"]=>
  string(5) "CLERK"
  ["MGR"]=>
  string(4) "7902"
  ["HIREDATE"]=>
  string(9) "17-DEC-80"
  ["SAL"]=>
  string(3) "800"
  ["COMM"]=>
  NULL
  ["DEPTNO"]=>
  string(2) "20"
}
array(8) {
  ["EMPNO"]=>
  string(4) "7369"
  ["ENAME"]=>
  string(5) "SMITH"
  ["JOB"]=>
  string(5) "CLERK"
  ["MGR"]=>
  string(4) "7902"
  ["HIREDATE"]=>
  string(9) "17-DEC-80"
  ["SAL"]=>
  string(3) "800"
  ["COMM"]=>
  NULL
  ["DEPTNO"]=>
  string(2) "20"
  ["PIC"]=>
  NULL
}

Actual result:
--------------
array(8) {
  ["EMPNO"]=>
  string(4) "7369"
  ["ENAME"]=>
  string(5) "SMITH"
  ["JOB"]=>
  string(5) "CLERK"
  ["MGR"]=>
  string(4) "7902"
  ["HIREDATE"]=>
  string(9) "17-DEC-80"
  ["SAL"]=>
  string(3) "800"
  ["COMM"]=>
  NULL
  ["DEPTNO"]=>
  string(2) "20"
}
<br />
<b>Warning</b>:  PDOStatement::fetch() [<a href='function.fetch'>function.fetch</a>]: SQLSTATE[HY000]: General error: 1405 OCIStmtFetch: ORA-01405: fetched column value is NULL
 (..\pecl_5_0\pdo_oci\oci_statement.c:446) in <b>C:\dev\tests\db.php</b> on line <b>13</b><br />
bool(false)