The errors that PHP throws can sometimes be confusing and mysterious. It outputs them in an effort to make debugging your scripts easier so you can go and correct the error. To help with deciphering them, we have created a guide by looking at the source code for PHP versions: 4.0.0, 4.0.6, 4.1.2, 4.2.3, 4.3.6 and 5.0.0RC2. versions 4.3.6 and 5.0.0RC2.
On the tool they've created, all you need to do is enter in the error code number that the script spits back and it will show you the relevant information. It also has a listing of some of the samples below it to help you narrow it down quickly if you already know what you're looking for.
The site and the tool are all in French.