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?

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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.