You can get at the contents with "string_var = ifx_get_blob($blob_id);" if you choose to get the BLOBs in memory (with: "ifx_blobinfile(0) ;").
For insert/update queries you must create these "blob id's" yourself with "ifx_create_blob() ;". You then plug the blob id's into an array, and replace the blob columns with a question mark (?) in the query string. For updates/inserts, you are responsible for setting the blob contents with ifx_update_blob().