PDO offers three different error-handling modes

Pdo::errmode_silent

This is the default mode. PDO will simply set the error code and use the Pdo::errorcode () and Pdo::errorinfo () methods to examine the statements and database objects. If the error is caused by a call to the statement object, you can call the Pdostatement::errorcode () or Pdostatement::errorinfo () method of that object. If the error occurs because of a call to a database object, you can invoke both methods on the database object.

Pdo::errmode_warning

In addition to setting the error code, PDO will emit a traditional e_warning message. This setting is useful during debugging/testing if you just want to see what's going on and don't interrupt the application's process.

Pdo::errmode_exception (Note: It will throw an exception inside itself, end-of-page)

In addition to setting the error code, PDO throws a Pdoexception exception class and sets its properties to reflect the error code and error message. This setting is also useful during debugging because it effectively magnifies the points in the script that produce the error, so that you can quickly point out potential areas of the code that are problematic (remember: If the exception causes the script to terminate, the transaction is automatically rolled back).

Exception mode Another very useful is that, compared to traditional PHP style warnings, you can build your own error handling more clearly, and the exception pattern requires less code/nesting than silent mode and explicitly checking the return value of each database call.

PDO offers three different error-handling modes