Pro PHP- Patterns, Frameworks, Testing and More

CHAPTER 4 ■ EXCEPTIONS^35

Listing 4-3. Throwing a Custom Exception

function connectToDatabase() {

if(!$conn = pg_connect(...)) {

throw new DatabaseException("Friendly Message");

}

}

try {

connectToDatabase();

} catch(DatabaseException $e) {

echo $e->getMessage(). "\n";

echo $e->getDatabaseErrorMessage();

}

When thrown, this exception generates the following message:

Friendly Message

Unable to connect to PostgreSQL server: Access Denied for user...

This example exposes not only a friendly message, but also the technical details of why the

connection failed. In most circumstances, you will wish to hide the technical details in a produc-

tion environment, and expose the technical error message only when debugging.

Logging Exceptions

It is often advantageous to log exceptions to a file for later review. You can accomplish this in

either of two ways:

• Create a custom exception base class for your application.


• Define an uncaught exception handler.

Let’s look at both techniques.

Logging Custom Exceptions

To define a logging base class, you need to subclass Exception and add a log() method. Place

a call to this logging method in your overridden constructor. Listing 4-4 demonstrates how to

create this logging method.

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