The Contact_Vcard classes for PHP allow you to parse and build vCards that match the IMC standards.
A vCard is a plain text file that contains an "electronic business card" of contact information suitable for including in an address book. The vCard format is a standardized way of trading personal and organizational contact information.
For a full overview of the vCard 3.0 specification, refer to Internet Engineering Task Force RFC 2426.
For a full overview of the vCard 2.1 specification (version 2.1), refer to the Internet Mail Consortium Product Developer Information web page.