PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

194 Chapter 7 Error and Exception Handling
The constructor for this class takes two parameters: a message and a code.They are
intended to represent an error message and an error code number. Both of these parameters
are optional.
Finally, underneath your try block, you need at least one catch block.A catch block
looks like this:
catch (typehint exception)
{
// handle exception
}
You can have more than one catch block associated with a single try block. Using
more than one would make sense if each catch block is waiting to catch a different type
of exception. For example, if you want to catch exceptions of the Exception class, your
catch block might look like this:
catch (Exception $e)
{
// handle exception
}
The object passed into (and caught by) the catch block is the one passed to (and
thrown by) the throw statement that raised the exception.The exception can be of any
type, but it is good form to use either instances of the Exception class or instances of
your own user-defined exceptions that inherit from the Exception class. (You see how
to define your own exceptions later in the chapter.)
When an exception is raised, PHP looks for a matching catch block. If you have
more than one catch block, the objects passed in to each should be of different types so
that PHP can work out which catch block to fall through to.
One other point to note is that you can raise further exceptions within a catch block.
To make this discussion a bit clearer, let’s look at an example. A simple exception handling
example is shown in Listing 7.1.
Listing 7.1