How to avoid dynamic properties in PHP (raise an Error when setting an undeclared property)

Question

Example:

error_reporting(E_ALL | E_STRICT);
class Test {}
$obj = new Test();
$obj->undeclared = "oops";    // I want an error here !! :(
echo $obj->algo;              // oops 

I tested it on PHP 5.2.11 and 5.3.0.

I don't want dynamic properties in my objects.
Is possible to force PHP to raise an ERROR in that situation ?

Answer 1

Use __set() ?

<?php
class Test {

    public $bar;

    public function __set($name, $value) {
        throw new Exception('Cant set!');
    }
}

$obj = new Test;
$obj->bar = 'foo';
$obj->foo = 'evil';
?>

Answer 2

A bit more diligence with your error message and you can help your own coding. Having the following as your base class setup will:

1. protect uses of this class from overwriting your properties
2. protect misspellings of variables (especially camel-case mistakes) for instance $this->callerID returns as expected but $this->callerId throws an exception and prevents code errors.

    public function __set($name,$value) {
        switch ($name) {
            default:
                // we don't allow any magic properties set or overwriting our properties
                try {
                    $error = "Assignment of {$name} in " . static::class . ' not allowed because it is a magic variable or read-only property.';
                    throw new \RuntimeException($error);
                } catch ( \RuntimeException $e ) {
                    echo 'Caught exception: ' . $e->getMessage() . PHP_EOL;
                }

        }
    }

    public function __get($name)
    {
        switch ($name) {
            default:
                // we don't allow any magic properties
                try {
                    $error = "var {$name} is not a property of " . static::class . '.';
                    throw new \RuntimeException($error);
                } catch ( \RuntimeException $e ) {
                    echo 'Caught exception: ' . $e->getMessage() . PHP_EOL;
                }
        }
        return null;
    }

    public function __isset($name)
    {
        switch ($name) {
            default:
                return false;
        }
    }

Answer 3

By "I don't want dynamic properties in my objects." I assume you mean that you don't want your object variables to ever be undefined? If this is the case then just instantiate all of your class variables. You can even make them static if you're really concerned about them being constant as opposed to dynamic in any way.

If you attempt to access an object variable that does not exist, then PHP will throw an error. The answer that radmen suggested would actually make it so that instead of throwing an error, PHP would dynamically create undefined object variables for you on the fly.