Gregory Szorc writes today about a fact that's only recently come true in PHP's handling of errors - it seems that it now returns proper HTTP status codes when a problem comes up.
If it encounters a serious error, like a parse error, it just stops and there is nothing you can do about it. If this happens on a hosted web site, you get a blank page served with the HTTP status code of 200. Completely useless to remote connections.
This fix will be included in the next version of PHP - the upcoming 5.2.4 release.