The difference between public, private and protected in php class and example analysis_PHP tutorial

1. The difference between public, private and protected
public: has the greatest permissions and can be called internally, instance called, etc.
protected: protected type, used for calling this class and inherited classes.
private: Private type, only used in this class.

2, Example

Copy code The code is as follows:

error_reporting(E_ALL);
class test{
public $public;
private $private;
protected $protected;
static $instance;
public function __construct(){
$this->public = 'public
';
$this->private = 'private
';
$this- >protected = 'protected
';
}
static function tank(){
if (!isset(self::$instance[get_class()]))
{
$c = get_class();
self::$instance = new $c;
}
return self::$instance;
}  
public function pub_function() {
echo "you request public function
";
echo $this->public;
echo $this->private; //private, can be called internally
echo $this-> ;protected; //protected, can be called internally
$this->pri_function(); //private method, can be called internally
$this->pro_function(); //protected method, can be called internally
}
protected function pro_function(){
echo "you request protected function
";
}
private function pri_function(){
echo "you request private function";
}
}
$test = test::tank();
echo $test->public;
echo $test->private; //Fatal error: Cannot access private property test::$private
echo $test->protected; //Fatal error: Cannot access protected property test::$protected
$test->pub_function();
$test->pro_function(); //Fatal error: Call to protected method test::pro_function() from context
$test->pri_function(); //Fatal error: Call to private method test: :pri_function() from context
?>

From the above example, we can see that
public: can be called internally in a class or instantiated.
private: Can be called inside the class, and an error will be reported when instantiating the call.
protected: It can be called inside the class, and an error will be reported when instantiating the call.

Copy code The code is as follows:

class test{
 public $public;
 private $private;
 protected $protected;
 static $instance;
 public  function __construct(){
 $this->public    = 'public    
';
 $this->private   = 'private   
';
 $this->protected = 'protected 
';
 }
 protected function tank(){                          //私有方法不能继承，换成public,protected
 if (!isset(self::$instance[get_class()]))
 {
 $c = get_class();
 self::$instance = new $c;
 }
 return self::$instance;
 }    
 public function pub_function() {
 echo "you request public function
";
 echo $this->public;
 }
 protected  function pro_function(){
 echo "you request protected function
";
 echo $this->protected;
 }
 private function pri_function(){
 echo "you request private function
";
 echo $this->private;
 }
}
class test1 extends test{
 public function __construct(){
 parent::tank();
 parent::__construct();
 }
 public function tank(){
 echo $this->public;
 echo $this->private;       //Notice: Undefined property: test1::$private
 echo $this->protected;
 $this->pub_function();
 $this->pro_function();
 $this->pri_function();    //Fatal error: Call to private method test::pri_function() from context 'test1'
 }
 public  function pro_extends_function(){
 echo "you request extends_protected function
";
 }
 public function pri_extends_function(){
 echo "you request extends_private function
";
 }
}
error_reporting(E_ALL);
$test = new test1();
$test -> tank();       //子类和父类有相同名字的属性和方法，实例化子类时，子类的中的属性和方法会盖掉父类的。
?>

从上面的例子中，我们可以看出，
public:    test中的public可以被继承。
private:   test中的private不可以被继承。
protected：test中的protected可以被继承。
static：   test中的static可以被继承。
唉，对于这些东西，老是不喜欢记着，用的时候，总感觉不对，又要去查，所以写个例子，方便自己查看。

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