Returns the POID for the element specified by oid (if any). If oid is invalid, or the specified oid has no POID, the function returns a null string. If the operation is successful, the function returns the POID for the oid.

A POID can have two document objects when the POID is a reference to a file entity. The POID will always have a document object handle for the contents of the file entity being referenced. If the reference POID itself is a top-level sibling in another object, it will also have a document object handle for that object.

If oid is a file entity reference, omitting obj or setting obj to a value of 0 specifies that oid_poid will return the document object handle of the contents of the file entity. If oid is a file entity reference, setting obj to a value of 1 specifies that oid_poid will return the document object handle of the reference POID.

If oid is not a file entity reference, obj is ignored.