Fatal error: Call to undefined function stripunicode()

Hello,

I have the template page name page-tag.php for display the page with all tags like this: http://www.nhadep.net/vi/tu-khoa/

Beside that, i'm using the function to call some tags at the widget, like this: http://s145.photobucket.com/user/dragonanhtuan/media/4-14-20144-00-10PM_zpse2141c92.jpg.html

The function is: <?php wp_tag_page(''); ?>

Everything works fine.

Then, i'm developing new page here: http://www.export2global.net/emo/

I'm using the template page page-tag.php again but when i created the page with template page-tag, the page display this error:
Fatal error: Call to undefined function stripunicode() in /hsphere/local/home/c285130/export2global.net/emo/**********/page-tag.php on line 57

Please help me take a look.

If you want to view file page-tag.php or view my error page please let me know.

Thank you,
Tuan.