Under Windows odbc_connect (and PDO ODBC) apparently uses the Windows locale to handle input and output from e.g. MS access and MS SQL Server databases.

This causes lots of headaches if one is using other than ASCII characters.

Work-round solutions like utf8_encode and mb_convert both fails.

The solution I fund working is to perform the following changes to Windows

Control Panel > Region > Administrative > Change system locale
>Check '<i>Use Unicode UTF-8 for worldwide language support.</i>'

One additional note regarding odbc_pconnect  and possibly other variations of pconnect:

If the connection encounters an error (bad SQL, incorrect request, etc), that error will return with  be present in odbc_errormsg for every subsequent action on that connection, even if subsequent actions don't cause another error.

For example:

A script connects with odbc_pconnect.
The connection is created on it's first use.
The script calls a query "Select * FROM Table1".
Table1 doesn't exist and odbc_errormsg contains that error.

Later(days, perhaps), a different script is called using the same parameters to odbc_pconnect.
The connection already exists, so it is reused.
The script calls a query "Select * FROM Table0".
The query runs fine, but odbc_errormsg still returns the error about Table1 not existing.

I'm not seeing a way to clear that error using odbc_ functions, so keep your eyes open for this gotcha or use odbc_connect instead.

As always Microsoft is clueless... I've been trying to connect to an Access database on a W2K on the network (not a local file, but mapped on the V: drive), via ODBC.

All I got is this message:
Warning: SQL error: [Microsoft][ODBC Microsoft Access Driver] '(unknown)' is not a valid path. Make sure that the path name is spelled correctly and that you are connected to the server on which the file resides., SQL state S1009 in SQLConnect in d:\apache\cm\creaart.php on line 13

So... I started looking al around and looks like the ODBC driver has some severe problems:

1. It cannot access a Access database via a mapped drive. And this is for ANY application, name it PHP, Coldfusion, whatever
2. You cannot make a system DSN with a UNC (\\Server\resource), so you must map the drive

Cute isn't it?

So... I quit on ODBC and went via ADO, this is the code that works:

=== CODE ===

$db = '\\\\server\\resource\\db.mdb';
$conn = new COM('ADODB.Connection');
$conn->Open("DRIVER={Driver do Microsoft Access (*.mdb)}; DBQ=$db");

// Driver do Microsoft Access (*.mdb)
// must be the name in your odbc drivers, the one you get
// from the Data Sources (ODBC).
// In this case, I'm in Mexico but the driver name is in portuguese, thanks Microsoft.

$sql = 'SELECT username FROM tblUsuarios';
$res = $conn->Execute($sql);
while (!$res->EOF)
{
    print $res->Fields['username']->Value . "<br>";
    $res->MoveNext();
}

$res->Close(); 
$conn->Close(); 
$res = null; 
$conn = null;

=== /CODE ===