please help error on functions.php

[09-Jun-2012 19:50:12] PHP Warning:  array_diff() [<a href='function.array-diff'>function.array-diff</a>]: Argument #1 is not an array in /home/*******/public_html/incfiles/classes/functions.php on line 339
[09-Jun-2012 19:50:12] PHP Warning:  implode() [<a href='function.implode'>function.implode</a>]: Invalid arguments passed in /home/********/public_html/incfiles/classes/functions.php on line 339

public static function display_menu($val = array(), $delimiter = ' | ', $end_space = '')
    {
        return implode($delimiter, array_diff($val, array(''))) . $end_space;
    }

echo functions::display_menu(array('<a href="">ONE</a>', '<a href="">TWO</a>'));

L!MP (09.06.2012/20:36)
The first argument (@var) should be an array:

echo functions::display_menu(array('<a href="">ONE</a>', '<a href="">TWO</a>'));