PHP: Calling a user-defined function inside constructor?

Question

I have a class userAuth inside its constructor I have added code to check the user is valid or not, if there is no value in session then I check cookies (as a part of "Remember Me" feature), if there is some value inside cookies then I call a function ConfirmUser to check its authenticity from database. On the basis of value returned by the confirmUser function I am returning a bool (true or fales) value in constructor.

I have created my class as:

<?php
    class userAuth {

        function userAuth(){
            //code
        }

        function confirmUser($username, $password){
                   //code
        }
    }

    $signin_user = new userAuth();

?>

confirmUser function take two string type parameters and return return a integer value of 0, 1, 2.

I can't add code of confirmUser function inside the constructor as I am using this function at some more places in my application.

So, I want to know how to call a user-defined function inside constructor in PHP. Please help.

Thanks!

Put some code in question. There is no difference where to call function. — zerkms
– zerkms, Commented Dec 2, 2010 at 13:46
Ensure include/require for function declaration of confirmUser, and you can call confirmUser inside constructor...what is the problem? — ajreal
– ajreal, Commented Dec 2, 2010 at 13:47
You said you're returning a bool in the constructor which is a bit strange. A constructor cannot return anything but an instance of its class. Can you elaborate? — Teekin
– Teekin, Commented Dec 2, 2010 at 14:20

DampeS8N · Accepted Answer · 2010-12-02 13:55:24Z

30

$this->nameOfFunction()

But when they are in a class, they are called Methods.

answered Dec 2, 2010 at 13:55

DampeS8N

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1 Comment

Colin Fine Over a year ago

I suspect you thought that until the constructor was complete, there wasn't a '$this' to call methods on; but there is. In PHP the new object exists, and '$this' points to it, as soon as it enters the constructor.

adsc · Accepted Answer · 2017-06-26 10:49:13Z

9

Be careful with using $this in a constructor, though, because in an extension hierarchy, it can cause unexpected behaviour:

<?php

class ParentClass {
    public function __construct() {
        $this->action();
    }

    public function action() {
        echo 'parent action' . PHP_EOL;
    }
}

class ChildClass extends ParentClass {
    public function __construct() {
        parent::__construct();
        $this->action();
    }

    public function action() {
        echo 'child action' . PHP_EOL;
    }
}

$child = new ChildClass();

Output:

child action
child action

Whereas:

class ParentClass {
    public function __construct() {
        self::action();
    }

    public function action() {
        echo 'parent action' . PHP_EOL;
    }
}

class ChildClass extends ParentClass {
    public function __construct() {
        parent::__construct();
        self::action();
    }

    public function action() {
        echo 'child action' . PHP_EOL;
    }
}

$child = new ChildClass();

Output:

parent action
child action

answered Jun 26, 2017 at 10:49

adsc

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1 Comment

Anupam Over a year ago

Thanks for explaining this very important difference between this and self::

Mark N Hopgood · Accepted Answer · 2020-01-30 15:39:35Z

3

There is no difference between calling a function inside a constructor and calling from somewhere else. If the method is declared in the same class you should use $this->function()

By the way, in php5 you are suggested to name your constructor like this:
function __construct()

If not then put public keyword before your constructor definition like this public function userAuth()

edited Jan 30, 2020 at 15:39

Mark N Hopgood

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answered Dec 2, 2010 at 13:45

Caner

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Comments

Shakti Singh · Accepted Answer · 2010-12-02 13:58:52Z

2

you can call with $this

<?php
    class userAuth {

        function userAuth($username, $password){
             $this->confirmUser($username, $password);
        }

        function confirmUser($username, $password){
                   //code
        }
    }

    $signin_user = new userAuth($username, $password);

?>

answered Dec 2, 2010 at 13:58

Shakti Singh

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