iconv error detection

I'm writing a lightweight webmail in PHP, Dolda Webmail (<http://sf.net/projects/doldawebmail>), and I'm having some trouble with the iconv function provided by PHP. The problem is that when it encounters a multibyte sequence that cannot be decoded (like in an erroneously encoded message), it just stops there and returns the string up to that point, and I have not been able to find out any way of detecting that an error has indeed occurred. This is causing me a great deal of trouble... Does iconv provide a way of detecting if an error has occurred, and if so, how? Thanks for your attention! Fredrik Tolf