


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
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< br>";
}
}
$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.
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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