How do I add a method to an object in PHP?

Question

I've got an Object Oriented library I wanted to add a method to, and while I'm fairly certain I could just go into the source of that library and add it, I imagine this is what's generally known as A Bad Idea.

How would I go about adding my own method to a PHP object correctly?

UPDATE ** editing **

The library I'm trying to add a method to is simpleHTML, nothing fancy, just a method to improve readability. So I tried adding to my code:

class simpleHTMLDOM extends simple_html_dom { public function remove_node() { $this->outertext = ""; } }

which got me: Fatal error: Call to undefined method simple_html_dom_node::remove_node(). So obviously, when you grab an element in simpleHTML it returns an object of type simple_html_dom_node.

If I add the method to simple_html_dom_node my subclass isn't what will be created by simplHTML ... so stuck as to where to go next.

Could you add the code that is instantiating the object and calling the remove_node() method? — Niels Bom
– Niels Bom, Commented Jan 27, 2010 at 21:59

Pascal MARTIN · Accepted Answer · 2010-01-27 17:32:09Z

A solution would be to create a new class, that extends the one from your library -- and, then, use your class, which have have all methods of the original one, plus yours.

Here's a (very quick and simple) example :

class YourClass extends TheLibraryClass { public function yourNewMethod() { // do what you want here } }

And, then, you use your class :

$obj = new YourClass(); $obj->yourNewMethod();

And you can call the methods of the TheLibraryClass class, as yours inherits the properties and methods of that one :

$obj->aMethodFromTheLibrary();

About that, you can take a look at the Object Inheritance section of the manual.

And, as you guessed, modifying a library is definitly a bad idea : you'll have to re-do that modification each time you update the library !

(One day or another, you'll forget -- or one of your colleagues will forget ^^ )

Thanks, still having issues, made an edit above. Honestly just dropping my method into the source works but I'd like to do it "right" if I can.

Gordon · Accepted Answer · 2010-01-28 00:45:02Z

You could do it with inheritance, but you could also use a decorator pattern if you do not need access to any protected members from SimpleHtml. This is a somewhat more flexible approach. See the linked page for details.

class MySimpleHtmlExtension { protected $_dom; public function __construct(simple_html_dom $simpleHtml) { $this->_dom = $simpleHtml; } public function removeNode(simple_html_dom_node $node) { $node->outertext = ''; return $this; } public function __call($method, $args) { if(method_exists($this->_dom, $method)) { return call_user_func_array(array($this->_dom , $method), $args)); } throw new BadMethodCallException("$method does not exist"); } }

You'd use the above like this

$ext = new MySimpleHtmlExtension( new simple_html_dom ); $ext->load('<html><body>Hello <span>World</span>!</body></html>'); $ext->removeNode( $ext->find('span', 0) );

Here's the problem - the method actually gets called on a simple_dom_html_node object - which is created by the simple_dom_html object. I don't think there's a solution.

GSto · Accepted Answer · 2010-01-27 17:33:12Z

0

I don't why adding the method would be bad, however if you want to so without editing the library, your best bet would be to extend the class like so:

class NewClass extends OldClass { function newMethod() { //do stuff } }

answered Jan 27, 2010 at 17:33

GSto

42.5k37 gold badges136 silver badges188 bronze badges

2 Comments

Tyler Carter Over a year ago

Adding the method is bad because if you update the library, or the library changes its internal implementation, you are very apt to have compatibility issues.

Stomped Over a year ago

Yep, but I can't get this to work by extending the class, so far. Hopefully someone can help based on my edits.

prodigitalson · Accepted Answer · 2010-01-27 17:34:39Z

class myExtenstionClass extends SomeClassInLibrary { public function myMethod() { // your function definition } }

As Pascal suggests... read the manual :-)

Collectives™ on Stack Overflow

How do I add a method to an object in PHP?

4 Answers 4

1 Comment

1 Comment

2 Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

1 Comment

2 Comments

Comments

Related