Why am I missing the symbol "_xmlNodeListGetString" when using the PayPal API?

When I add the PayPal API to my iPhone application, I'm seeing the following errors:

  "_xmlNodeListGetString", re开发者_运维技巧ferenced from:
  "_inflateInit_", referenced from:
  "_xmlSetProp", referenced from:

What could be the cause of these?

Looks like you are missing the libxml2 framework.

1. Right Click on the Frameworks Group in the xcode sidebar
2. Choose Add/Existing Frameworks...
3. Select libxml2.dylib in the framework list that just opened.
4. Hit Add
5. Rebuild project

Be sure to add the "-lxml2" flag to your Linker flags and "/usr/include/libxml2" to the Header Search Paths