Are abstract class constructors not implicitly called when a derived class is instantiated?

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轻奢々
轻奢々 2021-01-30 19:38

Take this example:

abstract class Base {
    function __construct() {
        echo \'Base __construct
\'; } } class Child extends Base { funct
3条回答
  •  -上瘾入骨i
    2021-01-30 20:40

    No, the constructor of the parent class is not called if the child class defines a constructor.

    From the constructor of your child class, you have to call the constructor of the parent's class :

    parent::__construct();
    

    Passing it parameters, if needed.

    Generally, you'll do so at the beginning of the constructor of the child class, before any specific code ; which means, in your case, you'd have :

    class Child extends Base {
        function __construct() {
            parent::__construct();
            echo 'Child __construct
    '; } }


    And, for reference, you can take a look at this page of the PHP manual : Constructors and Destructors -- it states (quoting) :

    Note: Parent constructors are not called implicitly if the child class defines a constructor.
    In order to run a parent constructor, a call to parent::__construct() within the child constructor is required.

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