Question

I have a PHP Class which requires a unique value in its constructor. If multiple instances of the same class are passed the same value the results are horrific.

How would I go about detecting other instances of a Class so I can check and prevent this from happening before constructing any new ones?

Answer 1

A simple solution would be to keep a static array of the values inside the class. Then, when a new instance is created, check the static array’s contents in the constructor.

Something like..

class Foo {
    private static $usedValues = array();

    public function __construct($val) {
        if(in_array($val, self::$usedValues)) {
            throw new Exception('blah');
        }

        self::$usedValues[] = $val;
    }
}