I'm extending Bankrekening and adding the variable $rente to it, the value of $rente should be determined by the function BerekenRente() which doesn't use any parameters and doesn't need to be initialized in the constructor parameters from my understanding. I get this error:
Parse error: syntax error, unexpected '(', expecting variable (T_VARIABLE) in C:\xampp\htdocs\SpaarBetaalrekening.php on line 55
This would refer to this line: public function __construct($naam, $rekeningnummer, $saldo, $kredietlimiet) {
class Spaarrekening extends Bankrekening{
    var $rente;
    public function __construct($naam, $rekeningnummer, $saldo, $kredietlimiet) {
        $this->naam = $naam;
        $this->rekeningnummer = $rekeningnummer;
        $this->saldo = $saldo;
        $this->kredietlimiet = $kredietlimiet;
        $this->rente = BerekenRente();
    }
    //Ontvang rente
    function OntvangRente(){
        $this->saldo = $saldo + BerekenRente();
    }
    function BerekenRente(){
        return ($this->saldo / 100) * 0.30;
    }
}
$rekening1 = new Spaarrekening("James", 5543, 600, 2000);
echo $rekening1->saldo;
