Unable to log in to administrator dashboard

Hello
When I install the active-directory-authentication plug in, I am not able to login to my administrator dashboard. Moreover I cannot deactivate this plug in. It gets me the following error 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 tried to follow all the commands on your link above but it was not giving me the access. At this moment all I want to deactivate the plug in and want to access again to administration area.
Need your help.
Please give me a solution. Thanks in advance.
