Next, continue to bite the bullet down .... ：）
Type indication
In PHP5, you can indicate in a method of a class that its arguments must be an instance of a class:
Example 10: type instance
class Foo {
Code ...
}
Class Bar {
Public Function Process_a_foo (foo $foo) {
Some Code
}
}
$b = new Bar ();
$f = new Foo ();
$b->process_a_foo ($f);
?>
As you can see, specifying a class name before the variable lets PHP5 know that the variable will be an instance of a class
Static members
Static members and static methods are commonly referred to in OOP as "class variables" and "class methods."
A "class method" can be invoked when the object is not instantiated
A "class variable" can be accessed when the object is not instantiated (and does not require the method of the object to invoke)
Example 11: Class variables and class methods
Class Calculator {
static public $pi = 3.14151692;
static public function Add ($x, $y) {
return $x + $y;
}
}
$s = calculator:: $pi;
$result = Calculator::add (3,7);
Print ("$result");
?>
* Exception Handling
Exception handling is an accepted method of handling exception errors in the development language, such as in Java and C + +.
PHP5 uses the "Try" and "catch" keywords to catch exceptions.
Example 12: Exception Handling
class Foo {
function Divide ($x, $y) {
if ($y ==0) throw new Exception ("Cannot divide by zero");
return $x/$y;
}
}
$x = new Foo ();
try {
$x->divide (3,0);
} catch (Exception $e) {
echo $e->getmessage ();
echo "\ n
\ n ";
Some catastrophic measure here
}
?>
As you can see, "Try" represents the place where the code executes, and the code that executes the "catch" area when there is an error.
In the "Catch" area you should specify the object that executes the exception, which will make our structure clearer
Custom Exception Handling
You can define your own custom code for catching exception errors in your program.
Very simple, you just need to inherit an exception class, in which you need a constructor and a method called GetMessage:
Example 13: Custom Exception class
Class Weirdproblem extends Exception {
Private $data;
function Weirdproblem ($data) {
Parent::exception ();
$this->data = $data;
}
function GetMessage () {
Return $this->data. "caused a weird exception!";
}
}
?>
You can now throw exceptions with "throw new Weirdproblem ($foo)". If an exception occurs in a zone such as try{}, PHP5 will jump in
Catch area to throw an exception.
Name space
namespaces allow you to easily invoke a set of classes or methods:
Example 14: namespaces
Namespace Math {
Class Complex {
.... Code ...
function __construct () {
Print ("Hey");
}
}
}
$m = new Math::complex ();
?>
Note: In real-world applications, you can define classes with the same name in different namespaces to accomplish different tasks (but the interfaces are the same)
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