Exceptions in PHP5

• PHP5 supports Exception model, like C++/C# and Java.

syntax to catch exception:

try {
//code which can launch an exception
// [...]
// manual exception throw
throw new Exception("thrown exception");
//not executed ! (throw command is caught below
print "not printed!";
}
catch(Exception $e) { print $e->getMessage();}

this code prints : "thrown exception".

It's possibile to throw an exception inside a catch construct. The new exception will be caught in the external try-catch block.

try {
try{
throw new Exception("internal exception");
}
catch (Exception $e) { throw new Exception($e->getMessage()); }
print "not printed!";
}
catch(Exception $e) { print $e->getMessage(); }

This code prints: "internal exception"

Structure of "Exception" built-in class and inheritance

class Exception
{
protected $message = 'Unknown exception'; // exception message
protected $code = 0; // user defined exception code
protected $file; // source filename of exception
protected $line; // source line of exception

function __construct($message = null, $code = 0);

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

/* Overrideable */
function __toString(); // formatted string for display
}

In case of extension, remember to call the superclass constructor in the extended class constructor

parent::__construct()

Multiple catch constructs

It's allowed to specify more than one catch after a try construct.

If the exception doesnt' match with the argument, it will be caught to the next catch block.

Note: an Exception object match also with the objects of its subclasses. Mind the order !

class MyException extends Exception {/* ...*/ }

try{
throw new MyException("");
}
catch (MyException $e) {// <-- match ! executed !
print "MyException";
}
catch (Exception $e) { // never executed
print "Exception";
}

And ...

try{
throw new MyException("");
}
catch (Exception2 $e) { print "Exception"; }
catch (Exception $e) { // <-- match ! executed !
print "Exception";
}
catch (MyException $e) { print "MyException"; }