Cannot initialize an uninitialized variable inside a class method

Question

I have just started practicing OO programming using PHP. Recently I have encountered a problem.

I am trying to declare a variable inside a class, but leaving it uninitialized. Later inside a method of the class when I try to initialize the variable it shows the following errors:

Undefined variable: a in C:\wamp\www\sample.php on line 6

Fatal error: Cannot access empty property in C:\wamp\www\sample.php on line 6

Here is the code that I am trying to execute:

<?php
    class Sample{
        public $a;

        function call($b){
            $this->$a = $b;
            echo $a;
        }
    }

    $sam = new Sample();
    $sam->call(5);
?>

How do I fix this?

Possible duplicate of [PHP Fatal error: Cannot access empty property](http://stackoverflow.com/questions/14920216/php-fatal-error-cannot-access-empty-property) — Ken Y-N, Oct 14 '16 at 07:57

score 1 · Accepted Answer · edited Jul 06 '19 at 18:27

1

In the function call, $a does not exist. Only $this->a (without $ before the a), which is the property of your "sam" object, and $b, which is an input parameter. Plus when you set the property, you must not use $a. Use $this->a.

If you would have a variable which contains a property name of the class, you should use $this->$a, which would mean $this->asdf, if $a = 'asdf';

edited Jul 06 '19 at 18:27

Peter Mortensen

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answered Oct 14 '16 at 07:57

OlajosCs

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Got it!! Thanks!! – Asutosh Rana Oct 14 '16 at 08:07

score 1 · Answer 2 · edited Jul 06 '19 at 18:26

1

The correct syntax is $this->a, not $this->$a.

edited Jul 06 '19 at 18:26

Peter Mortensen

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answered Oct 14 '16 at 07:58

dimlucas

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Cannot initialize an uninitialized variable inside a class method

2 Answers2