My Php Validation doesn't work when inside FB Canvas iframe

I have server side php validation for a form. When I put this form in the canvas iframe and it stopped working corr开发者_如何学编程ectly.

if (is_array($this->post('variable')))

The code above is an if statement and even if the parameters are true it still goes to else if. Has anyone experienced this problem?

Please note that the first iframe run will get post variables from the Facebook. You may not expect the post vars before the form is created.