OO PHP question regarding arrays

Question

I'm trying to learn object oriented PHP by porting some of the simple exercises I've learnt in Java to PHP. This is one of them, to calculate the total salary of 3 people.

I'm apparently having a problem with the array in the family class - php gives an error about "Undefined variable: a_family" on line 32. Could anybody point me in the correct direction?

<?php
    class person {
        private $name;
        private $salary;

        //constructor
        function __construct($given_name, $given_salary) {
            $this->name = $given_name;
            $this->salary = $given_salary;
        }

        //getter for salary
        function get_salary() {
            return $this->salary;
        }

    }

    class family {
        private $a_family;

        function __construct() {
            $a_family = array();
        }

        function add_family_member($given_person) {
            $a_family[] = $given_person;
        }

        function get_total_salary() {
            $total_salary = 0;
            foreach ($a_family as $member) {
                $total_salary = $total_salary + $member->get_salary();
            }

            return $total_salary;
        }
    }

    $mum = new person("Mummy", 500);
    $dad = new person("Daddy", 1500);
    $sis = new person("Sister", 20);

    $my_family = new family();

    $my_family->add_family_member($mum);
    $my_family->add_family_member($dad);
    $my_family->add_family_member($sis);

    $family_income = $my_family->get_total_salary();

?>

<!-- start HTML -->
<html>
    <head>

    </head>

    <body>
        <p>My total family income is $<?php echo $family_income; ?>.</p>
    </body>

</html>

ah i see! thanks everyone for your responses. much appreciated! :) — kit
– kit, Commented Nov 5, 2009 at 3:40
FYI, you should pick an answer that answered your question, assuming one has. — cletus
– cletus, Commented Nov 5, 2009 at 4:16

cletus · Accepted Answer · 2009-11-05 03:28:40Z

2

You want:

$this->a_family = array();

and:

$this->a_family[] = $given_person;

just like you've done in the first class.

answered Nov 5, 2009 at 3:28

cletus

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Comments

Asaph · Accepted Answer · 2009-11-05 03:30:27Z

1

Unlike java, in PHP the this keyword is mandatory for referencing instance variables even when there is no ambiguity. You've done it correctly in your person class. You need to use this in your family class too.

$this->a_family = array();

...

$this->a_family[] = $given_person;

...

foreach ($this->a_family as $member) {

...

answered Nov 5, 2009 at 3:30

Asaph

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Comments

BraedenP · Accepted Answer · 2009-11-05 03:29:02Z

1

You need to be referencing $a_family as $this->a_family instead within your functions.

answered Nov 5, 2009 at 3:29

BraedenP

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Comments

mauris · Accepted Answer · 2009-11-05 03:29:04Z

1

You need:

$this->a_family

because you a referring to a variable in the class scope, even if you have set $a_family to private.

$a_family only refers to the variable in the current method.

answered Nov 5, 2009 at 3:29

mauris

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