Try fixing Apache or WordPress error-Collection of common programming errors

I have the following error message in the error log file of my website. Can you explain me what it means, is there security problem? How could I fix it?

[Mon Feb 25 21:04:34 2013] [error] [client 173.199.116.83] PHP Parse error: syntax error, unexpected T_VARIABLE in /Mywebsite/wp-includes/functions.php on line 192

[Mon Feb 25 20:48:01 2013] [error] [client 80.118.73.90] PHP Parse error: syntax error, unexpected T_VARIABLE in /Mywebsite/wp-includes/functions.php on line 192, referer: http://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDQQFjAA&url=http%3A%2F%2Fwww.banahan.fr%2F&ei=4r8rUfSBAYe2hQevjICABg&usg=AFQjCNHbl8fe0yvfJH0lEdTBUNw1FYw1tA&sig2=7PRr2vM5qj9DuX64oZXwwQ&bvm=bv.42768644,d.ZG4

[Mon Feb 25 19:37:42 2013] [error] [client 91.207.4.186] PHP Parse error: syntax error, unexpected T_VARIABLE in /Mywebsite/wp-includes/functions.php on line 192, referer: http://glavprofit.ru/

[error] [client 217.13.55.146] PHP Fatal error: require_once() [function.require]: Failed opening required ‘/Mywebsite/wp-admin/includes/plugin.php’ (include_path=’.:/Library/Tenon/PHP/lib/php’) in /Mywebsite//wp-includes/update.php on line 144