Simple Facebook Wall Post Error

I am trying to integrate the Simple Facebook Wall Post into my website. I have followed all of the directions in the readme file; however, when I load the page, I get the following error:

"warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'simple_fbwall_post_button' not found or invalid function name in /home/secretha/public_html/includes/form.inc on line 378."

I have the Application ID, I've installed Boxy, I've enabled the module, I've set the permissions, and I've pasted the code into a page.tpl file.

I should note that when I posted the original code in the readme, I received a critical PHP error. I had to add a ")" at the end of one of the arrays to solve the error. I did not change any other part of the code.

I hope someone can help.