What are the access control characters of php?

php's access control symbols are: 1. public, set the property or method to be accessible from anywhere; 2. private, set the property or method to be accessible only by its own class or object; 3. Protected, sets a property or method to be accessible by its class or its descendants.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Access control modifier list

Access modifier	Meaning
Public	Set a property or method to be accessible from anywhere
Private	Set a property or method to be accessible only by its own class or object
Protected	Set a property or method to be accessible by its class or its descendants

public

Public properties and methods can be accessed from anywhere.

<?PHP
class Book {
        public $Name;
        public function say() {
                print "PHP!\n";
        }
}
class PythonBook extends Book {
        public function say() {
                print "Python!\n";
        }
}
$aBook = new PythonBook;
$aBook->Name = "Python";
print $aBook->Name;
?>

By default, all class methods are public.

The above code generates the following results.

private

Private properties can only be accessed within their own class.

<?PHP
class Book {
        private $Name;
        private $NameTag;
        public function setName($NewName) {
                // etc
        }
}
?>

Subclasses cannot access private parent methods and properties. If you want to do this, you need the protected keyword.

Protected

Protected properties and methods are accessible within their own class and subclasses. Consider the following code:

<?PHP
class Book {
        public $Name;
        protected function getName() {
                return $this->Name;
        }
}
class Poodle extends Book {
        public function say() {
                print ""Book", says " . $this->getName();
        }
}
$aBook = new Poodle;
$aBook->Name = "PHP";
$aBook->say();
?>

The above code generates the following results.

Example

The code below shows how to use Private members to hide information.

<?php
  class Widget
  {
    private $name;
    private $price;
    private $id;
    public function __construct($name, $price)
    {
      $this->name = $name;
      $this->price = floatval($price);
      $this->id = uniqid();
    }
    //checks if two widgets are the same
    public function equals($widget)
    {
      return(($this->name == $widget->name) AND
       ($this->price == $widget->price));
    }
  }
  $w1 = new Widget("Cog", 5.00);
  $w2 = new Widget("Cog", 5.00);
  $w3 = new Widget("Gear", 7.00);
  //TRUE
  if($w1->equals($w2))
  {
    print("w1 and w2 are the same<br>\n");
  }
  //FALSE
  if($w1->equals($w3))
  {
    print("w1 and w3 are the same<br>\n");
  }
  //FALSE, == includes id in comparison
  if($w1 == $w2)
  {
    print("w1 and w2 are the same<br>\n");
  }
?>

The above code generates the following results.

Recommended study: "PHP Video Tutorial"

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