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

User-Defined Exceptions
197
Listing 7.2
Continued
}
final function getFile() {
return $this->file;
}
final function getTrace() {
return $this->trace;
}
final function getTraceAsString() {
return self::TraceFormat($this);
}
function _toString() {
return $this->string;
}
static private function StringFormat(Exception $exception) {
// ... a function not available in PHP scripts
// that returns all relevant information as a string
}
static private function TraceFormat(Exception $exception) {
// ... a function not available in PHP scripts
// that returns the backtrace as a string
}
}
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The main reason we are looking at this class definition is to note that most of the public
methods are final:That means you cannot override them.You can create your own subclass
Exceptions, but you cannot change the behavior of the basic methods. Note that
you can override the __toString() function, so you can change the way the exception
is displayed. You can also add your own methods.
An example of a user-defined Exception class is shown in Listing 7.3.
Listing 7.3 user_defined_exception.php—An Example of a User-Defined
Exception Class