PHP - Assigning class constant value to property in constructor

Question

I have been trying to create a simple class, which defines default property values as class constants at the top of the class definition.

However, my code does not seem to be assigning the value of the constant to the property in the constructor.

class Tester {
    const DEFAULT_VAL = 500;

    private $val;

    public function __construct() {
        $val = self::DEFAULT_VAL;
    }

    public function show_val() {
        echo "DEFAULT_VAL is " . self::DEFAULT_VAL . "<br />";
        echo "val is " . $val;
    }
}

$obj = new Tester();
$obj->show_val();

Running the code above yields the result:

const is 500
val is

I cannot figure out why I cannot assign the predefined, constant default value to the property from within the constructor.

Paul · Accepted Answer · 2012-01-08 17:09:03Z

6

You need to use $this->val in place of $val in two places in your code, since each instance of Tester has it's own val:

class Tester {

    const DEFAULT_VAL = 500;

    private $val;

    public function __construct() {
        $this->val = self::DEFAULT_VAL;
    }

    public function show_val() {
        echo "DEFAULT_VAL is " . self::DEFAULT_VAL . "<br />";
        echo "val is " . $this->val;
    }
}

$obj = new Tester();
$obj->show_val();

Outputs:

DEFAULT_VAL is 500
val is 500

answered Jan 8, 2012 at 17:09

Paul

142k28 gold badges285 silver badges272 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

djentastic Over a year ago

I knew it was going to be something simple. Haven't done much OOP in PHP, but thanks for the quick response!

hakre Over a year ago

You can define the default value for a property, see stackoverflow.com/a/8779542/367456

hakre · Accepted Answer · 2012-01-08 17:20:07Z

3

As long as the default value is a constant (expression), you can just note that down in the definition of the property:

class Tester
{
    const DEFAULT_VAL = 500;

    private $val = self::DEFAULT_VAL;

    public function __construct() {
    }
}

That done it's already set when the object get's constructed, so you don't have to write code to set it. Demo.

answered Jan 8, 2012 at 17:20

hakre

200k55 gold badges454 silver badges866 bronze badges

2 Comments

djentastic Over a year ago

Good to know, appreciate the response. However I am doing this in the constructor because I intend to allow this value to be explicitly set in the constructor, otherwise use the default value.

hakre Over a year ago

Which would be why you predefine it above the constructor. You can still change it.

Collectives™ on Stack Overflow

PHP - Assigning class constant value to property in constructor

2 Answers 2

2 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related