Parse error: syntax error, unexpected '$this' (T_VARIABLE)

I was experiencing strange error "Parse error: syntax error, unexpected '$this' (T_VARIABLE) in /httpdocs/app/code/core/Mage/Catalog/Model/Abstract.php on line 116 with my php codes which is properly executed in my local machine. This happens when I upload files via FTP.

I have done a detailed investigation and I could see a random string "^Mt" appears in the mentioned line which has caused the error. I have manually removed this string and the problem is solved. I would like to know how...

Parse error: syntax error, unexpected '$this' (T_VARIABLE)