1 <?php
 2 class MyClass {
 3     static $a = 0;
 4     function getValue(){
 5         return self::$a;
 6     }
 7 }
 8
 9 $obj = new MyClass();
10 echo $obj->getValue() . PHP_EOL;
11
12 echo MyClass::$a . PHP_EOL;
13 ?>

<?phpclass MyClass {static $count = 0;public $unique_id;function __construct(){self::$count++;$this->unique_id = self::$count;}}$obj1 = new MyClass();echo $obj1->unique_id . PHP_EOL;$obj2 = new MyClass();echo $obj2->unique_id . PHP_EOL;
?>

 1 <?php
 2     class HelloWorld {
 3         static function sayHello(){
 4             print "Hello World";
 5             self::printNewLine();
 6         }
 7
 8         static function printNewLine(){
 9             echo PHP_EOL;
10         }
11     }
12     HelloWorld::sayHello();
13     HelloWorld::sayHello();
14 ?>

<?phpclass MyColorEnumClass {const RED = "red";const GREEN = "green";const BLUE = "blue";static function printColor(){print self::RED . PHP_EOL;print self::GREEN . PHP_EOL;print self::BLUE . PHP_EOL;}}        MyColorEnumClass::printColor();
?>

<?phpclass MyClass {public $var = 1;}$obj1 = new MyClass();//$obj2 = $obj1;$obj2 = clone $obj1;$obj2->var = 2;//使用$obj2 = $obj1, 下面输出2//使用$obj2 = clone $obj1, 下面输出1echo $obj1->var . PHP_EOL;?>

<?phpclass Cat{function miao(){echo "cat";}}class Dog{function wang(){echo "dog";}}function printTheRightSound( $obj ){if( $obj instanceof Cat ) {$obj->miao();}else if ( $obj instanceof Dog ) {$obj->wang();}else {echo "传递了错误的对象类型";}echo PHP_EOL;}printTheRightSound( new Cat() );printTheRightSound( new Dog() );
?>

 1 <?php
 2     abstract class Animal {
 3         abstract function makeSound();
 4     }
 5     class Cat extends Animal{
 6         function makeSound(){
 7             echo "cat";
 8         }
 9     }
10     class Dog extends Animal{
11         function makeSound(){
12             echo "dog";
13         }
14     }
15     class Chicken extends Animal {
16         function makeSound(){
17             echo "chicken";
18         }
19     }
20
21     function printTheRightSound( $obj ){
22         if( $obj instanceof Animal ) {
23             $obj->makeSound();
24         }else {
25             echo "传递了错误的对象类型";
26         }
27         echo PHP_EOL;
28     }
29
30     printTheRightSound( new Cat() );
31     printTheRightSound( new Dog() );
32     printTheRightSound( new Chicken() );
33 ?>