php oop inheritance 101 question, why does my child class have two values for the same static variab-CodePudding

the code is self-explanatory, but the problem is, that I can't override the static variable through method calls, so the static variable of the class gives a value, but the value that I get through the objects is different.

Class dbEntity {

    protected static $connection;
    private static $name = "dbEntity";

    public static function getName() {
        return self::$name;
    }
    public static function setConnection($connection) {
        self::$connection = $connection;
    }
    public static function getConnection() {
        return self::$connection;
    }
}

Class Patient extends dbEntity {
    public static $connection = "patientConnection";
    public static $name = "Patient";
}

$p = new Patient();

$p->setConnection("myConnection");

echo $p->getConnection() . "\n"; //myConnection
echo Patient::$connection . "\n"; //patientConnection
echo $p->getConnection() . "\n"; //myConnection

CodePudding user response：

Ulrich is correct, if you change the following lines from self:: to static:: the code works as you're expecting it to.

    public static function getName() {
        return static::$name;
    }
    public static function setConnection($connection) {
        static::$connection = $connection;
    }
    public static function getConnection() {
        return static::$connection;
    }

...

echo $p->getConnection() . "<br>"; //myConnection
echo Patient::$connection . "<br>"; //myConnection
echo $p->getConnection() . "<br>"; //myConnection

CodePudding user response：

You need late static binding, see the official documentation: https://www.php.net/manual/en/language.oop5.late-static-bindings.php