I get a parse error - unexpected ; at line x message. What is this?

This means that there is a syntax error in your PHP - you have not written valid code.

Typically you may have placed either two semi-colons at the end of a line or placed one where there shouldn't be.

 If you have been using echo or print statements then you may not have closed the print statement correctly.

It is quite a descriptive error so you know where it is, but you may need to look at the surrounding lines to see if something there is what is causing the parse error.