133544 PHP Script Fix

I am getting the following errors on my site when I login. Warning: session_start() [function.session-start]: The session id contains invalid characters, valid characters are only a-z, A-Z and 0-9 in /home/digitalm/public_html/members/[login to view URL] on line 2 Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/digitalm/public_html/members/[login to view URL]) in /home/digitalm/public_html/members/[login to view URL] on line 2 Warning: session_destroy() [function.session-destroy]: Session object destruction failed in /home/digitalm/public_html/members/[login to view URL] on line 3 Warning: session_start() [function.session-start]: The session id contains invalid characters, valid characters are only a-z, A-Z and 0-9 in /home/digitalm/public_html/members/[login to view URL] on line 4 Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/digitalm/public_html/members/[login to view URL]) in /home/digitalm/public_html/members/[login to view URL] on line 4 Warning: Cannot modify header information - headers already sent by (output started at /home/digitalm/public_html/members/[login to view URL]) in /home/digitalm/public_html/members/[login to view URL] on line 21 Warning: Unknown(): The session id contains invalid characters, valid characters are only a-z, A-Z and 0-9 in Unknown on line 0 Warning: Unknown(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in Unknown on line 0 I need this fixed quickly. Please include details in bid.