Can’t Log on to Admin Dashboard after Plugin installation

Hello buddies,
After installing the Active-Directory-Authentication Plugin, I can't seem to log on to my Administrator Dashboard and consequently, I can't deactivate the Plugin itself.
I get the following message:
Fatal error: Call to undefined function ldap_connect() in /home/xxx/public_html/mysite.com/wp-content/plugins/active-directory-authentication/ad_ldap/adLDAP.php on line 105
I have tried the instructions provided but to no success. I need to deactivate the plugin to access my site administration area.
Do you, guys, know how I can do this? Please reply if you do.
Thanks.
