To transfer binary information via XML-RPC we need to encode the data in base64 (serialization) and use the base64 tags as xml tags.

Example Declaration:

<param>
<value>
<base64>UHSYDhD1423Cc0Ad3NVP4OidTd8E1kRY5Edh</base64>
</value>
</param>

Since PHP does not have a binary data type, developers need to encode files in base64 for XML-RPC transfer by using the file_get_contents function.