PHP Code: usage of this keyword

Question

public function __construct($template = '', array $data = array())
{
    if ($template !== '') {
        $this->setTemplate($template);
    }
    if (!empty($data)) {
        foreach ($data as $name => $value) {
            $this->$name = $value;
        }
    }
}

Got this from the devshed composite view tutorial (http://www.devshed.com/c/a/PHP/PHP-Composite-View-Design-Pattern-Introducing-the-Key-Concepts/1/). Anyway, I'm a bit confuse on, $this->$name = $value; statement.

I usually use $this for class's properties and/or when invoking class's methods within the said class. Plus the statement have two $'s. Which is weird! So is $this->$name = $value referring to the $name defined in the foreach loop? If so can someone explain this usage or logic behind this?

Thank you in advance.

mrwooster · Accepted Answer · 2010-12-14 09:39:28Z

2

The $name in

$this->$name = $value

Sets the variable defined as $name to $value

E.g. if $name = 'user', then this is the equivalent to

$this->user = value;

This type of syntax is often used (as demonstrated above) in foreach loops to set object values.

Note: Each time $this->variable_name is called, if 'variable_name' is not already defined as a property of the object, the magic __set function is called, with 'variable_name' passed as the argument.

See http://php.net/manual/en/language.oop5.overloading.php

edited Dec 14, 2010 at 9:39

answered Dec 14, 2010 at 9:32

mrwooster

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3 Comments

KingCrunch Over a year ago

Here right, but only true, if name does not exists as real property. In this case the magic properties are not called.

mrwooster Over a year ago

@KingCrunch - Yes, this is true, will edit my response to make it a bit clearer

mythicalprogrammer Over a year ago

I think I got it. After messing around with the AbstractView class. It seems that $this->$name is referring to a dynamically created $name by __set. So if say, a class property isn't explicitly define in the class, a user can basically do: $foo = new AbstractView; $foo->bar = 'stuff';, so that the __set function is called and create a bar class property to the abstractview class. And $this->$name = $value statement is referring to the $name variable, a place holder, that is used in the other magic methods defined through out the AbstractView class, hence the extra $. Thank you so much!

Teej · Accepted Answer · 2010-12-14 09:34:24Z

1

I didn't go to the link you posted but reading the code.

I will give you an example:

// If $data has the following values
array(
    'firstname' => 'my first name',
    'surname'  => 'my surname'
)

The code will have 'firstname' and 'surname' as a public property of the class. The values for $this->firstname will be 'my first name'. The value of $this->surname will be 'my surname'.

answered Dec 14, 2010 at 9:34

Teej

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Comments

Shakti Singh · Accepted Answer · 2010-12-14 09:33:09Z

0

$name contain the name of property nothing else

instead of just mentioning the property statically it is pointing to the variable which contain the name of property

$name='someproperty';

$this->$name;

answered Dec 14, 2010 at 9:33

Shakti Singh

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Comments

Oliver A. · Accepted Answer · 2010-12-14 09:34:10Z

0

Let as assume that the current value of $name is "foo". then $this->name will return exactly the same as $this->foo.

answered Dec 14, 2010 at 9:34

Oliver A.

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1 Comment

Alin P. Over a year ago

You mean $this->$name. And not return, but rather refer.

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