Remover Elementos de uma lista

Olá pessoal, como posso fazer uma função para remover elementos da minha lista?

<?php

$lista = new Lista();
$lista->add( new Cliente( 'Guedes' ) );

echo $lista->get()->getName() , PHP_EOL."<br>";;

?>
 

<?php

interface DoubleLinkedListItem {

 public function hasNext();
 public function hasPrevious();
 public function next();
 public function previous();
 public function setNext( DoubleLinkedListItem $next );
 public function setPrevious( DoubleLinkedListItem $previous );
}

abstract class AbstractListItem implements DoubleLinkedListItem {
/**
* @var ListItem
*/

 private $next;

 /**
 * @var ListItem
 */
 private $previous;

 public function hasNext(){
 return !is_null( $this->next );
 }

 public function hasPrevious(){
 return !is_null( $this->previous );
 }

 public function next(){
 if ( $this->hasNext() ){
 return $this->next;
 } else {
 throw new RuntimeException( 'Não temos um próximo' );
 }
 }

 public function previous(){
 if ( $this->hasPrevious() ){
 return $this->previous;
 } else {
 throw new RuntimeException( 'Não temos um anterior' );
 }
 }

 public function setNext( DoubleLinkedListItem $next ){
 $this->next = $next;
 }

 public function setPrevious( DoubleLinkedListItem $previous ){
 $this->previous = $previous;
 }
}

interface Clients {

 public function getName();
 // public function getAddress();

}

class Cliente extends AbstractListItem implements Clients {

 private $name;

 public function __construct( $name ){
 $this->name = $name;
 }

 public function getName(){
 return $this->name;
 }
}

class DoubleLinkedList {

 private $first;
 private $last;
 private $current;

 public function add( DoubleLinkedListItem $item ){
 if ( is_null( $this->first ) ){
 $this->first = $item;
 } elseif ( !is_null( $this->last ) ){
 $item->setPrevious( $this->last );
 $this->last->setNext( $item );
 }

 $this->last = $item;
 }

 public function getFirst(){
 if ( !is_null( $this->first ) ){
 return $this->first;
 } else {
 throw new RuntimeException( 'Lista vazia.' );
 }
 }

 public function getLast(){
 if ( !is_null( $this->last ) ){
 return $this->last;
 } else {
 throw new RuntimeException( 'Lista vazia.' );
 }
 }

 public function get(){
 if ( is_null( $this->current ) ){
 $this->current = $this->getFirst();
 } else {
 $this->current = $this->current->next();
 }

 return $this->current;
 }
}

?>