@Override
	public boolean removeFirstOccurrence(Object elem) {
		int index = indexOf(elem);
		if (index == -1) {
			return false;
		}
		doRemove(index);
		return true;
	}
Helper method for adding multiple elements to the list.
This default implementation calls doAdd() for adding each element.

@param index index where element should be added
             (-1 is valid for adding at the end)
@return      true if elements have been added, false otherwise
jphp-runtime/src/php/runtime/memory/support/IList.java