Problem:
Working on a non-cachable (using header("Expires: 0"); et. al. ) php file, when you make a mistake (forgot the ; for example) the "Parse error: ..." response is sent back. This response does not have the HTTP headers that mark it as non-cachable.

IE, will keep that page in cache and it associates this page with the url. So every time I hit that page it get the cached "Parse error:..." page even though I fixed the error. The user is forced to hit the refresh button to see the real page.

Solution:
PHP errors that do not give a chance for any HTTP headers to be sent back ( i.e. "Parse error:.. ") should send back the response with HTTP cache headers set to expire the page right away. In other words, they should always send header("Expires: 0"); 

Take care :)
Ahmad