Execute a method when an instance variable is referenced in a PHP class?

Question

Is it possible to run a function when referring to a variable in a php class rather than simply returning its value, similar to javascript's ability for a variable to hold a method?

class LazyClassTest()
{

    protected $_lazyInitializedVar;

    public function __construct()
    {
        /* // How can this call and return runWhenReferrenced() when
           // someone refers to it outside of the class:
           $class = new LazyClass();
           $class->lazy;
           // Such that $class->lazy calls $this->runWhenReferrenced each
           // time it is referred to via $class->lazy?
         */
        $this->lazy = $this->runWhenReferrenced();
    }

    protected function runWhenReferrenced()
    {
        if (!$this->_lazyInitializedVar) {
            $this->_lazyInitializedVar = 'someValue';
        }

        return $this->_lazyInitializedVar
    }

}

mplappert · Accepted Answer · 2011-01-12 16:17:55Z

2

PHP5s magic method __get($key) and __set($key, $value) might be what you need. More information about them is available in the PHP manual.

edited Jan 12, 2011 at 16:17

answered Jan 12, 2011 at 16:11

mplappert

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2 Comments

Rafid Over a year ago

Hmmm... not all of us understand German, so why not share the English manual? :-)

cjroth Over a year ago

While this is not what I was looking for, I actually ended up using it and it helped, so thanks!

Gekkie · Accepted Answer · 2011-01-12 17:00:26Z

1

This sounds like PHP5.3: lambda / closures / anonymous functions

http://php.net/manual/en/functions.anonymous.php:

<?php
$greet = function($name) {
    printf("Hello %s\r\n", $name);
};

$greet('World');
$greet('PHP');
?>

answered Jan 12, 2011 at 17:00

Gekkie

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Comments

NikiC · Accepted Answer · 2011-01-12 16:17:27Z

1

You are probably heading in the wrong direction. You normally want to define a getter getLazyVar(). There is a reason why people always make properties protected and defined getters / setters: So they can pre- or postprocess the values.

answered Jan 12, 2011 at 16:17

NikiC

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1 Comment

cjroth Over a year ago

I agree that it's good practice to use the getLazyVar() practice but my reason for wanting a variable is to keep the class's pattern consistent with other similarly patterned classes that I have so that a method's properties will always be accessible in the exact same way.

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