从多个数组的特定元素求和

Page where I add elements into the basket

<?php

   session_start();

   include('link.php');

  



   if(!isset($_SESSION['basket'])){

    $_SESSION['basket']=[];

   }

   // $id_permit=$_POST['id_fp'];
   // $chosen_date=$_POST['date_permit'];
 

  
   $_SESSION['little_basket']= array (

   'itemIdPermit'=> "'".$_POST["id_fp"]."'",
   'itemChosenDate'=> "'".$_POST["date_permit"]."'",
   'itemFinalPrice'=> "'".$_POST["final_price"]."'",
   'itemFinalPriceNotDiscount'=>"'".$_POST["price_not_discount"]."'"
                                                        );
                                    

  // $_SESSION['basket'][] = $_SESSION['little_basket'];
  
   array_push($_SESSION['basket'], $_SESSION['little_basket']);

   print_r($_SESSION['basket']);

   // $_SESSION['basket']=[];

   // echo $_SESSION['basket'];



    // header('location:index.php?area=fishing_permit');

   
   

?>

Page where I show the contents of the basket

<?php

  // session_start();

  // include('link.php');
   // include('add_basket.php');

  // $ids = '';

   /* foreach($_SESSION['basket'] as $id){
    $ids = $ids . $id . ",";
    };*/



    $lista_de_items_no_carrinho = $_SESSION['basket'];





  

    ?>
    <ul id="list_product">
     
    <?php

  
     $basketLength=count($lista_de_items_no_carrinho);



    for($i=0;$i< $basketLength;$i++){



   $sqlListChosenPermits = "select * from type_of_permits
   where id_type_of_permit =".$lista_de_items_no_carrinho[$i]['itemIdPermit'];

   $outcomeListChosenPermits = $link->query($sqlListChosenPermits);

   $line = mysqli_fetch_assoc($outcomeListChosenPermits);



   ?>

    <li>
      <div class="box_info"><h4><?php echo utf8_encode($line['type']); ?></h4><br>Validity:&nbsp;<?php echo utf8_encode($line['validity']);?>&nbsp;-&nbsp;Price:&nbsp;€<?php echo utf8_encode($line['price_eur']); ?> </div>
        
            <div class="map">Map info</div>
               <div class="rules">Rules</div>
         
                <div class="permit_facsimile"><a href="<?php echo $line['map']; ?>">Permit facsimile</a></div>
                <div class="chosen_date"><?php echo trim ($lista_de_items_no_carrinho[$i]['itemChosenDate'], "'") ;?></div>
        <div class="price">Euro&nbsp;<?php 


        $var= trim ($lista_de_items_no_carrinho[$i]['itemFinalPrice'],"'");


        if (!empty($var) ){
          
          echo  ($var);

        } else {

          echo trim($lista_de_items_no_carrinho[$i]['itemFinalPriceNotDiscount'],"'");


          } ?></div>
    
        <div class="add_basket"><a href="remove_from_basket.php?id=<?php echo $lista_de_items_no_carrinho[$i]['itemIdPermit']?>"><i class="fa fa-shopping-cart"></i>Remove from the Basket</a></div>
        <input type="hidden" name="last_price" id="last_price" value="<?php 

  
        if (!empty($lista_de_items_no_carrinho[$i]['itemFinalPrice'])) {
          
          echo trim ($lista_de_items_no_carrinho[$i]['itemFinalPrice'],"'");

        } else {

          echo trim($lista_de_items_no_carrinho[$i]['itemFinalPriceNotDiscount'],"'");


          } ?>">

     </li>

     <?php

    }


?>


    
    </ul>


<p>Total price:<span class="total_price"><?php

$lista_de_items_no_carrinho = $_SESSION['basket'];

$listaPrice=$lista_de_items_no_carrinho[$i]['itemFinalPriceNotDiscount'];

 $basketLength=count($listaPrice);

 $sum=0;

for($k= 0; $k < $basketLength; $k++){

$sum += ($basketLength[$k]);

echo ($sum);

}?>


 </span></p>


    

   <div class="buying"><button type="submit"><i class="fa fa-shopping-cart"></i>Conclude the purchase</button></div>

   
</div>