When trying to change it,throw an exception.
I suppose a solution, for class properties, would be to :
__get
method to access that property, using the "fake" name__set
method so it throws an exception when trying to set that property.For variables, I don't think it's possible to have a read-only variable for which PHP will throw an exception when you're trying to write to it.
For instance, consider this little class :
class MyClass {
protected $_data = array(
'myVar' => 'test'
);
public function __get($name) {
if (isset($this->_data[$name])) {
return $this->_data[$name];
} else {
// non-existant property
// => up to you to decide what to do
}
}
public function __set($name, $value) {
if ($name === 'myVar') {
throw new Exception("not allowed : $name");
} else {
// => up to you to decide what to do
}
}
}
Instanciating the class and trying to read the property :
$a = new MyClass();
echo $a->myVar . '<br />';
Will get you the expected output :
test
While trying to write to the property :
$a->myVar = 10;
Will get you an Exception :
Exception: not allowed : myVar in /.../temp.php on line 19