restricted to extensions. You can trigger your own exceptions by
throwing an instance of the
User-thrown exceptions are useful because they allow you to integrate
the error handling for your own errors with exceptions thrown by PHP.
Inside your methods, you may still need to check a return value;
however, converting those errors into exceptions allows the developer
using your classes to know he can reliably trap all errors using a
This section covers when it’s appropriate to throw exceptions of your own, and also how to create and throw an exception. Chapter 10 contains an address book application that demonstrates, among other things, how to put these exception-handling techniques into practice.
There many categories of errors, and exceptions are not always an appropriate way to handle them in PHP. In general, there are three major groups:
You, the programmer, have made a mistake. For instance, you passed an incorrect number of arguments to a method.
Your code is okay, but there’s a problem with an external resource. For instance, your code uses an XML file from a third-party web site, but that file isn’t valid XML. Or, a person has tried to join your site, but has requested a username already in use.
Your code is failing because of a breakdown in communication with another process. For instance, you cannot connect to a third-party web ...