function array_length(arr) {
    var length = 0;
    for( i = 0; i < arr.length; i++) {
      if( arr[i] == 2 )
        length++;
    }
    return length;
  }

  var aChanged = new Array();

  function prChanged( pId ) {
    if( eval('document.shopcart.product'+pId+'.value') != eval('document.shopcart.prhid'+pId+'.value')) {
      aChanged[pId]=2;
    } else {
      aChanged[pId]=1;
    }
  }

  function payIt() {
    if( array_length(aChanged) > 0 ) {
      alert('Update eerst om de wijzigingen van de aantallen op te slaan!');
    } else {
      document.location='client.php';
    }
  }

  function checkPayMethod() {
    if( document.payMethod.type[0].checked || document.payMethod.type[1].checked ) {
      return true;
    } else {
      alert('Kies uw betaalwijze');
      return false;
    }
  }