i installed cacti following the INSTALL file but if i try to view cacti url it shows this error:

Warning: mb_ereg_replace(): mbregex compile err: premature end of regular expression in /var/www/html/cacti/include/config.php on line 43

Warning: mb_ereg_replace(): mbregex compile err: premature end of regular expression in /var/www/html/cacti/include/config.php on line 44

Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/cacti/include/config.php:43) in /var/www/html/cacti/include/config.php on line 67

Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/cacti/include/config.php:43) in /var/www/html/cacti/include/config.php on line 68

Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/cacti/include/config.php:43) in /var/www/html/cacti/include/config.php on line 69

Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/cacti/include/config.php:43) in /var/www/html/cacti/include/config.php on line 70

Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/cacti/include/config.php:43) in /var/www/html/cacti/include/config.php on line 71

Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /var/www/html/cacti/include/config.php:43) in /var/www/html/cacti/include/config.php on line 74

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /var/www/html/cacti/include/config.php:43) in /var/www/html/cacti/include/config.php on line 74

Warning: main(/adodb/adodb.inc.php): failed to open stream: No such file or directory in /var/www/html/cacti/include/config.php on line 103

Warning: main(): Failed opening '/adodb/adodb.inc.php' for inclusion (include_path='.:/usr/share/pear') in /var/www/html/cacti/include/config.php on line 103

Warning: main(/database.php): failed to open stream: No such file or directory in /var/www/html/cacti/include/config.php on line 104

Warning: main(): Failed opening '/database.php' for inclusion (include_path='.:/usr/share/pear') in /var/www/html/cacti/include/config.php on line 104

Warning: main(/functions.php): failed to open stream: No such file or directory in /var/www/html/cacti/include/config.php on line 105

Warning: main(): Failed opening '/functions.php' for inclusion (include_path='.:/usr/share/pear') in /var/www/html/cacti/include/config.php on line 105

Fatal error: Call to undefined function: db_connect_real() in /var/www/html/cacti/include/config.php on line 111

i'm not sure if it's cacti or php error anyone encountered the same problem?