在面向对象的php类中，$ this-> name = $ name是什么意思？

class User {

  public $name;

  public function __construct($name) {
    $this->name = $name;
  }

  public function sayHi() {
    echo "Hi, I am $this->name!";
  }
}

Can someone explain to me word by word, what is meant by $this->name=$name? I keep thinking like, $this goes into(hence the -> sign) name which is (hence the = sign) $name defined beforehand. Also I dont see the need of that function?

Could just go like this :

class User {

  public $name;

  public function sayHi() {
    echo "Hi, I am $name!";
  }
}

I'm out of idea thinking about this .. thanks in advance.

When you are creating a new instance of the class User with the __construct parameter $name, by $this->nameit is set to the $name property of the class. In your second example $name does not get any value because you are nowhere assigning any value to it.

You could also have it like this for better understanding:

class User {

  public $nameProperty;

  public function __construct($name) {
    $this->nameProperty = $name;
  }

  public function sayHi() {
    echo "Hi, I am $this->nameProperty!";
  }
}

$this refers to the class you are currently in. So when you create a new class of User, you can pass a name by using the $name parameter. This parameter then gets assigned to the $nameProperty and in your method sayHi() you would then echo the assigned name.

class User {

   public $name; //declare a public property

   public function __construct($name) {
      $this->name = $name; 
     /* at the time of object creation u have to send the value & that value will be store into a public property which will be available through out the class. like $obj = new User('Harry'); Now this will be set in $this->name & it is available inside any method without declaration.

     */
   }

   public function sayHi() {
     echo "Hi, I am $this->name!"; //$this->name is available here
   }
}

In the context of a class method, when you want to access the class properties, you have to use $this->property. Without $this, you are actually accessing a variable in the scope of the method, which in your case, is the parameter $name.

The function __construct() is the constructor for your class object. So if you would instantiate an object, you would execute the code inside the constructor. Example:

$user = new User("John"); // you are actually calling the __construct method here
echo $user->name; // John

Hope that enlightens you.