When getting inherited from a parent class in PHP, especially in Codeigniter what does parent::__construct or parent::model() do?
How would it make difference if I don't __construct parent class?
And, which way is suggested?
-Added-
The focus is more on Codeigniter specific regarding a call to parent::__construct in different ways depending on versions and also if this could be omitted in case Codeigniter would do this automatically.
This is a normal class constructor. Let's look at the following example:
class A {
protected $some_var;
function __construct() {
$this->some_var = 'value added in class A';
}
function echo_some_var() {
echo $this->some_var;
}
}
class B extends A {
function __construct() {
$this->some_var = 'value added in class B';
}
}
$a = new A;
$a->echo_some_var(); // will print out 'value added in class A'
$b = new B;
$b->echo_some_var(); // will print out 'value added in class B'
As you see, class B inherits all values and functions from A. So the class member $some_var is accessible from A as well as from B. Because we've added a constructor in class B, the constructor of class A will NOT be used when you are creating a new object of class B.
Now look at the following examples:
class C extends A {
// empty
}
$c = new C;
$c->echo_some_var(); // will print out 'value added in class A'
As you can see, because we have not declared a constructor, the constructor of class A is used implicitly. But we can also do the following, which is equivalent to class C:
class D extends A {
function __construct() {
parent::__construct();
}
}
$d = new D;
$d->echo_some_var(); // will print out 'value added in class A'
So you only have to use the line parent::__construct(); when you want a constructor in the child class to do something, AND execute the parent constructor. Example given:
class E extends A {
private $some_other_var;
function __construct() {
// first do something important
$this->some_other_var = 'some other value';
// then execute the parent constructor anyway
parent::__construct();
}
}
More information can be found here: http://php.net/manual/en/language.oop5.php
private bugwhat does parent::__construct or parent::model() do?
these functions do exactly the same, only the construct function used to be named after the class itself prior to PHP5. I say in your example you are extending the Model class (and on some older version of CI since you don't need to use CI_model), if I'm correct in this __construct is the same as model().
It will simply execute the constructor of parent class
constructors.parent::__construct();. in other words: the child masks the parent constructor method, so you need to specify theparent::scope explicitly. So the answer to your question is: "That depends on what the parent constructor does, and if you need it"parent::__construct();when the application controller is initializing, you'll loseLoader and Coreclass and$this->loadwould never works. checksystem/core/Controller.phplines: 37-54.parent::__construct();is needed only if you want to declare__construct()method in your Controller which it will override the parent's one. That's true for models as well, but usingparent::__construct();in model just logs a debug message"Model Class Initialized", So if you need to know when Model is initialized (in logs), keep using that, If not, ignore it.