Question

In using PHP’s DOM classes (DOMNode, DOMEElement, etc) I have noticed that they possess truly readonly properties. For example, I can read the $nodeName property of a DOMNode, but I cannot write to it (if I do PHP throws a fatal error).

How can I create readonly properties of my own in PHP?

Answer 1

You can do it like this:

class Example {     private $__readOnly = 'hello world';     function __get($name) {         if($name === 'readOnly')             return $this->__readOnly;         user_error('Invalid property: ' . __CLASS__ . '->$name');     }     function __set($name, $value) {         user_error('Can't set property: ' . __CLASS__ . '->$name');     } } 

Only use this when you really need it – it is slower than normal property access. For PHP, it’s best to adopt a policy of only using setter methods to change a property from the outside.