Here are three basic types of runtime errors in PHP:
1. Notices: These are trivial, non-critical errors that PHP encounters
while executing a script - for example, accessing a variable that has
not yet been defined. By default, such errors are not displayed to the
user at all - although you can change this default behavior.
2. Warnings: These are more serious errors - for example, attempting to
include() a file which does not exist. By default, these errors are
displayed to the user, but they do not result in script termination.
3. Fatal errors: These are critical errors - for example, instantiating
an object of a non-existent class, or calling a non-existent function.
These errors cause the immediate termination of the script, and PHP's
default behavior is to display them to the user when they take place.
Internally, these variations are represented by twelve different error