paypal button does not display sizes after I add sizes to the products.php array and create foreach loop inside form.

<?php include("inc/products.php"); 

if (isset($_GET["id"])) {
    $product_id  = $_GET["id"];
    if (isset($products[$product_id])){ 
        $product = $products[$product_id]; 
    }
}
if (!isset($product)){
    header("Location: shirts.php");
    exit(); 
}

$section = "shirts"; 
$pageTitle = $product["name"];
include("inc/header.php");  ?>

        <div class="section page">

            <div class="wrapper">

                <div class="breadcrumb"><a href="shirts.php">Shirts</a> &gt; <?php echo $product["name"]; ?>
                </div>

                <div class="shirt-picture">
                        <span>  
                            <img src="<?php echo $product["img"];  ?>" alt="<?php echo $product["name"];  ?>">
                        </span> 
                </div>  

                <div class="shirt-details">
                    <h1><span class="price">$<?php echo $product["price"]; ?></span> <?php echo $product["name"]; ?></h1>




                    <form target="paypal" action="https://www.paypal.com/cgi-bin/webscr" method="post">
                    <input type="hidden" name="cmd" value="_s-xclick">
                    <input type="hidden" name="hosted_button_id" value="<?php echo $product["paypal"] ?>"; >

                    <table>
                    <tr>
                        <th>
                            <input type="hidden" name="on0" value="Size">
                            <label for="os0">Size</label>
                        </th> 
                        <td>
                            <select name="os0" id="os0">
                                <?php foreach($product["size"] as $size) { ?>
                                <option value="<?php echo $size; ?>"><?php echo $size; ?> </option>
                                <?php } ?>
                            </select> 
                        </td>
                    </tr>
                    </table>
                    <input type="submit" value="Add to Cart" name="submit">
                    </form>

                    <p class="note-designer">* All shirts are approved by George Akinian. </p>



                </div>

            </div>

        </div>

<?php include("inc/footer.php");

<?php


$products = array();
$products[101] = array(
    "name" => "Motley Crew",
    "img" => "img/shirts/shirt-101.jpg",
    "price" => 18,  
    "paypal" => "LREGR8T9KJVBL",
    "sizes" => array("Small", "Medium", "Large","X-Large")
);
$products[102] = array(
    "name" => "Logo Shirt,Black",
    "img" => "img/shirts/shirt-102.jpg",
    "price" => 20,
    "paypal"=> "4QJP28T7TVFM2",
    "sizes" => array("Small", "Medium", "Large","X-Large")
);
$products[103] = array(
    "name" => "Logo Shirt,Blue",
    "img" => "img/shirts/shirt-103.jpg",    
    "price" => 20,
    "paypal" => "NJLAHH9WNRU2W",
    "sizes" => array("Small", "Medium", "Large","X-Large")
);
$products[104] = array(
    "name" => "Logo Shirt,Green",
    "img" => "img/shirts/shirt-104.jpg",    
    "price" => 18,
    "paypal" => "Y7VGRU9NMS2CS",
    "sizes" => array("Small", "Medium", "Large","X-Large")
);
$products[105] = array(
    "name" => "Logo Shirt,Yellow",
    "img" => "img/shirts/shirt-105.jpg",    
    "price" => 25,
    "paypal" => "WX7BTHCKXXNQU",
    "sizes" => array("Small", "Medium", "Large","X-Large")
);
$products[106] = array(
    "name" => "Logo Shirt,Gray",
    "img" => "img/shirts/shirt-106.jpg",    
    "price" => 20,
    "paypal" => "QQ6SY3MZ2RR7Q",
    "sizes" => array("Small", "Medium", "Large","X-Large")
);
$products[107] = array(
    "name" => "Logo Shirt,Turquoise",
    "img" => "img/shirts/shirt-107.jpg",    
    "price" => 20,
    "paypal" => "J4UGJEFJRAQMU",
    "sizes" => array("Small", "Medium", "Large","X-Large")
);
$products[108] = array(
    "name" => "Logo Shirt,Orange",
    "img" => "img/shirts/shirt-108.jpg",    
    "price" => 25,
    "paypal" => "EYNAEAUEYTSH2",
    "sizes" => array("Large","X-Large")
);

?>