Post on wall
Request URL http://fan.yspan.com/
Request parameters:
| Parameter | Type | Required | Description |
| what | string | required | must have value "wall" |
| op | string |
required | must have value "put" |
| user_id | int | required | ID of the wall owner |
| message_body | string | required | the text you want to post on the wall |
| cat_id | int | optional | category ID for the post |
| embed_video | string or array of strings | optional | embed code for the video on this post |
| image_data | string | optional | base64 encoded image file |
| image_extension | string | required for image_data | the image extension for the sent data; accepted extensions: jpg, png, gif |