Unable to find function

[eluser]Philo01[/eluser]
Hi all,

I found this library:
http://pastebin.com/6E48Cfpc

And it callsback to a function, however I always get the error that the callback function does not exist.

Code:

$this->shortcode->add('footag', 'footag_func');
        $content = '[footag]';
        echo $this->shortcode->run($content);

A PHP Error was encountered

Severity: Warning

Message: call_user_func() expects parameter 1 to be a valid callback, function 'footag_func' not found or invalid function name

Filename: libraries/Shortcode.php

Line Number: 190