How to save multiple values in a variable?

You can save the sum in the session, so every time someone clicks the link to the page verify.php, the value of the variable "value" will be added to another variable "total value", saved in the session. / p>

ver.php

session_start();
$_SESSION['valor_total'] += $_GET['valor'];

echo $_SESSION['valor_total'];

PHP Func. session_start ()
PHP Sessions - W3Schools

You can pass multiple values to the same variable using straight parentheses []. This causes PHP to store the values in an array.

<a href ="verificar.php?valor[]=20&valor[]=30">Imagem</a>

PHP will receive the array array ('20 ',' 30 ') in $ _GET [' value '];

Well, without knowing more information it's hard to see what you want.

  

How to save multiple values in a variable?

Using an array (array) or an object.

$array = array('a', 'b', 'c'); //Array

//Objecto
$obj = new StdClass(); 
$obj->foo = 'bar';
$obj->baz = 'bazinga';

  

I'm creating a multi-product system, (...)   My question is: how to store this value in a variable, since it will have several products, and clicking on them will have to save the value and add them at the end ...

It seems to be wanting to make a shopping cart.

So it shows, if there is no javascript behind, your link will cause a redirect of the page. To avoid this you must use AJAX (Asynchronous Javascript and XML) in PT -> "Asynchronous Javascript and XML"

Example Code

A relatively simple way to make a shopping cart on a single page can be as follows:

  

cart.php

<?php
class Producto {
    public $id;
    public $nome;
    public $preco;
    public $quantidade = 0;

    public function __construct($id, $preco, $nome, $quantidade = 0) {
        $this->id = $id;
        $this->preco = $preco;
        $this->nome = $nome;
        $this->quantidade = $quantidade;
    }

    public function adicionar($quantidade = 1) {
        $this->quantidade = $this->quantidade + $quantidade;
    }

    public function remover($quantidade = 1) {
        $this->quantidade = $this->quantidade - $quantidade;
        if ($this->quantidade < 0)
            $this->quantidade = 0;
    }
}

class Carrinho implements IteratorAggregate {

    public $productosNoCarrinho = array();

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

    public function adicionar($id, $quantidade = 1) {
        if (!isset($this->productosNoCarrinho[$id]))
            return false;

        $this->productosNoCarrinho[$id]->adicionar($quantidade);
        return true;
    }

    public function remover($id, $quantidade = 1) {
        if (!isset($this->productosNoCarrinho[$id]))
            return false;

        $this->productosNoCarrinho[$id]->remover($quantidade);
        return true;
    }

    public function total() {
        $total = 0;
        foreach ($this->productosNoCarrinho as $prod) {
            $total += $prod->preco * $prod->quantidade;
        }
        return $total;
    }

    public function getIterator() {
        return new ArrayIterator($this->productosNoCarrinho);
    }

    public function mostrar() {
        $html = "<table><tr><td>#</td><td>Producto</td><td>Preco</td></tr>";
        foreach ($this->productosNoCarrinho as $producto) {
            if ($producto->quantidade > 0) {
                $html .= "<tr><td>{$producto->quantidade}</td>".
                "<td>{$producto->nome}</td>".
                "<td>".$producto->preco * $producto->quantidade."</td></tr>";
            }
        }
        $html .= "<tr><td></td><td></td><td>".$this->total()."</td></tr>";
        $html .= "</table>";
        return $html;
    }

    public function __toString() {
        return $this->mostrar();
    }
}

$listaDeProductos = array( 
    'A1' => new Producto('A1', 499, 'iPad air'),
    'A2' => new Producto('A2', 600, 'iPhone 5S'),
    'A3' => new Producto('A3', 1200, 'MacBook pro'),
    'A4' => new Producto('A4', 1100, 'iMac')
);

session_start();

if(!isset($_SESSION['carrinho'])) {
    $_SESSION['carrinho'] = new Carrinho($listaDeProductos);
}

$carrinho = $_SESSION['carrinho'];

if (isset($_GET['action'])) {
    if ($_GET['action'] == 'add' && isset($_GET['id'])) {
        $carrinho->adicionar($_GET['id']);
    } else if ($_GET['action'] == 'remove' && isset($_GET['id'])) { 
        $carrinho->remover($_GET['id']);
    }
    //print $carrinho->mostrar();
}
?>
<!DOCTYPE HTML>
<head>
<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>
</head>
<body>
<div id="lista-de-productos">
<h1>Productos</h1>
<ul>
    <?php foreach ($listaDeProductos as $prod) { ?>
        <li class="producto"
                data-id="<?=$prod->id?>"
                data-preco="<?=$prod->preco?>"
                data-nome="<?=$prod->nome?>"
        >
        <?=$prod->nome?> [<?=$prod->preco?>&euro;]
        <button class="adicionar">+</button>
        <button class="remover">-</button>
        </li>
    <?php } ?>
</ul>    
</div>
<hr>
<h1>Carrinho</h1>
<div id="carrinho">
<?=$carrinho?>
</div>
<script>
    $(document).ready( function() {
        var carrinhoID = $(this).attr("data-carrinhoID");

        $(document).on("click", ".producto .adicionar", function() {
            var prodID = $(this).parent().attr("data-id");
            $("#carrinho").load("carrinho.php?action=add&id=" +prodID +" #carrinho", function(responseText, textStatus, XMLHttpRequest) {
                //Sucesso
            });
        });

        $(document).on("click", ".producto .remover", function() {
            var prodID = $(this).parent().attr("data-id");
            $("#carrinho").load("carrinho.php?action=remove&id=" +prodID +" #carrinho", function(responseText, textStatus, XMLHttpRequest) {
                //Sucesso
            });
        });
    });
</script>
</body>
</html>

Explaining the code ...

What this code does is create a Cart (object of the Cart class) in the session. The control of the cart (and the price and total to pay) is done by the server but the action of add and remove is done by the browser through AJAX.

In terms of logic, what happens is as follows:

The HTTP VERB used is GET, but could be POST (incidentally, it made more sense). However, this is simpler to visualize.

ATTENTION: This code is for demonstration purposes only. SHOULD NOT BE USED IN PRODUCTION as it is INSECURE .