Extending Exceptions

    A User defined Exception class can be defined by extending the built-in Exception class. The members and properties below, show what is accessible within the child class that derives from the built-in Exception class.

    Example #1 The Built in Exception class

    <?php
    class Exception implements Throwable
    {
    protected     $message = 'Unknown exception'; // exception message
    private $string; // __toString cache
    protected $code = 0; // user defined exception code
    protected $file; // source filename of exception
    protected $line; // source line of exception
    private $trace; // backtrace
    private $previous; // previous exception if nested exception

    public function __construct($message = '', $code = 0, Throwable $previous = null);

    final private function     __clone(); // Inhibits cloning of exceptions.

    final public function getMessage(); // message of exception
    final public function getCode(); // code of exception
    final public function getFile(); // source filename
    final public function getLine(); // source line
    final public function getTrace(); // an array of the backtrace()
    final public function getPrevious(); // previous exception
    final public function getTraceAsString(); // formatted string of trace

    If a class extends the built-in Exception class and re-defines the constructor, it is highly recommended that it also call parent::__construct() to ensure all available data has been properly assigned. The __toString() method can be overridden to provide a custom output when the object is presented as a string.

    Note:

    Exceptions cannot be cloned. Attempting to clone an Exception will result in a fatal E_ERROR error.

    Example #2 Extending the Exception class

    <?php

    class MyException extends Exception
    {
    // Redefine the exception so message isn't optional
    public function __construct($message, $code = 0, Throwable $previous = null) {
    // some code

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