please help they hacked my site

[محروم.كوم]

Hi all
i have contacted the hosting company i'm hosted with and they told that some of my forum's files have been hacked and i don’t know what to do

could you please help me to take back my site

the errror is
Fatal error: Cannot redeclare pfzq() (previously declared in /home3/home2/public_html/forum/index.php(1) : eval()'d code:1) in /home3/home2/public_html/forum/includes/config.php(1) : eval()'d code on line 1

Again* i can't access the admincp __DEFINE_LIKE_SHARE__