Mssql doesn't see "strange" characters passed by php

The situation: PHP 5.2.9 => FreeTDS (a CVS version of July, if I remember well) => SQL 2008 R2. PHP is on a CentOS 5.x and Sql server on Windows 2008. Really funny :)

The problem: trying to pass a VARCHAR(2000) to a stored procedure, all goes well, until the string to be passed contains some strange (ok, not so strange) characters like

‘ , ’ the left/right single quotes

“ , ” the left/right double quotes

  , –

In presence of these characters, the stored procedure executes well, php doesn't report any error, but the field in the db comes out contai开发者_StackOverflow社区ning an empty string.

Removing these offending characters, the string is correctly parsed.

What to do?

Thank you in advance.

Converting Smart Quotes