I'm getting “String data, right truncation” errors from PHP using ODBC and connecting to a Microsoft SQL Server 2008R2 instance

Question

I am using PHP 5.3.3 on a CentOS 6.2 box, connecting to an instance of Microsoft SQL Server 2008R2. The connection works, and I am able to retrieve data, so long as my queries contain no parameters. When I add parameters, I get the error, "String data, right truncation".

Here's some example code:

<?php

$dbh = new PDO("odbc:myDSN", 'myUsername', 'myPassword');

$testCase = 1;
switch ($testCase) {
case 1:
  //  This case fails with this error:
  //    Error 22001: [Microsoft][ODBC Driver 11 for SQL Server]String data, right truncation (SQLExecute[0] at /builddir/build/BUILD/php-5.3.3/ext/pdo_odbc/odbc_stmt.c:254)
  $query = "select * from [myDatabase].[sys].[objects] WHERE (([name]=?))";
  $stmt = $dbh->prepare($query);
  $param1 = 'testtable1';
  $stmt->bindParam(1, $param1, PDO::PARAM_STR);   //  Note:  '1' is correct; it should not be '0'
  break;
case 2:
  //  This case works properly
  $query = "select * from [myDatabase].[sys].[objects] WHERE (([name]='testtable1'))";
  $stmt = $dbh->prepare($query);
  break;
}
$execResult = $stmt->execute();
if ($execResult) {
  print "Success!\n";
} else {
  $errorInfo = $stmt->errorInfo();
  print "Error " . $stmt->errorCode() . ": " . $errorInfo[2] . "\n";
}

$rowCount = 0;
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
  echo "Row " . $rowCount . ":\n";
  foreach ($row as $key => $value) {
    printf("  %-20s  %s\n", $key, $value);
  }
  $rowCount++;
}

Note that both test cases in the code above should do the same thing. Test case 1 uses parameters (as all code should), and test case 2 explicitly puts the relevant value in the SQL query. Test case 2 works. Test case 1 does not. I have tried replacing 'bindParam()' with 'bindValue()', but this has no effect. I've also tried using named parameters (e.g., :name) instead of positional parameters, but this also has no effect. I've tried adding an explicit length argument to bindParam() (using strlen($param1) as a value), but that gives a really bizarre error message (Incorrect syntax near 'OUTPUT'), and I can only assume that I'm doing it wrong. Integer parameters work properly. Only string parameters fail.

Any ideas why this isn't working?

Of course it's possible that there's a bug in the ODBC driver, or that it's not compatible with my version of PHP, or any number of similar problems, but I hope that I'm simply using the API improperly.

Edit:

Per Anda Iancu's suggestion, I delved into SQL Server Profiler. When traced, case 1 gives two nearly-identical records, one of class SQL:BatchStarting, and one of class SQL:BatchCompleted, both containing the text:

set fmtonly on select [name] from [myDatabase].[sys].[objects] where 1=2 set fmtonly off

Case 2 gives two records, both of class "RPC:Completed". The first contains the text:

declare @p1 int
set @p1=1
exec sp_prepexec @p1 output,NULL,N'select * from [myDatabase].[sys].[objects] WHERE (([name]=''testtable1''))'
select @p1

and the second contains the text:

exec sp_unprepare 1

---

Update:

In a desperate move, hoping there might be some kind of problem with dropping a new version of unixODBC into an existing version of PHP, I recompiled PHP from source. This turns out to be harder than you might think, on CentOS. Unfortunately, this had no effect. Same errors all around.

Answer 1

After much tweaking and searching, and a whole lot of shot-in-the-dark troubleshooting, I finally decided that this is an ODBC driver problem.

Specifically, I was using a driver downloaded from Microsoft, supposedly designed to work with PHP and unixODBC on RHEL/CentOS6. It's known as "Microsoft ODBC Driver 11 for SQL Server" in its own README file, and comes in a file called msodbcsql-11.0.2270.0.tar.gz. (These details provided for the benefit of anyone else trying to do the same thing)

In light of my experience, I do not recommend this driver.

I downloaded, compiled, and installed the latest "stable" version of FreeTDS instead. If it matters to you, the version I got is 0.91 (the download file doesn't say this, but it unpacks into a directory with this number). This had/has its own minor configuration problems, but ultimately seems to be working much better than the Microsoft-provided driver. I don't know if this is still being actively maintained, as the most recent timestamps in the distribution were August 17, 2011.

Silly me, thinking that I should use the Microsoft driver to access a Microsoft database server, and expect it to actually do what it says it will do.

Answer 2

I think you have probably encountered a bug in Microsoft's ODBC driver, but it is worth pointing out that pdo_odbc has a critical bug related to the bindValue() function. The bug only affects 64-bit but - ha! - Microsoft's ODBC driver is only 64-bit.

It's been a while, but I think which bug you hit depends on your data types and the SQL statement.