This will allow you to add the ability to order samples in Magento - and what better, it is the first version of the code I have found which works in 1.8!

orderSample.php

<?php
/**
 * WJB - Order Samples in Magento 1.8
 *
 * Upload this file to the root of your Magento installation and then you will
 * need to add the following snippet to your 'template/catalog/product/view.phtml'
 *
 * You may need to change some of the values below in the sample creation code
 * but this is all commented so it should be simple enough - my advice would be
 * to read through and edit where necessary

<input type="hidden" name="sample-sku" value="<?php echo $this->htmlEscape($_product->getSku()) ?>" /> 
<button type="button"
        onclick="sampleAddToCart(this)"
        class="lwd-button lwd-button-sample">
        <?php echo $this->__('Order Sample'); ?>
</button>
<script type="text/javascript">
function sampleAddToCart(sample)
{
    var do_continue = true;

    var sku = jQuery(sample).data('sku');

    jQuery('.required-entry[name^="super_attribute"]').each( function() {
        if( !jQuery(this).val() )
        {
            jQuery(this).addClass('validation-failed');
            jQuery(this).after('<div class="validation-advice" id="advice-required-entry-attribute">This is a required field.</div>');
            do_continue = false;
        }
    });

    if( do_continue )
    {
        console.log('lets go');
        jQuery('#product_addtocart_form')
                        .attr('action', '/orderSample.php' )
                        .submit();
    }

    return false;
}
</script>

 */
//////////////////////////////////////////////////////
// REQUIRE MAGE APP FOR ACCESSING MAGENTO FUNCTIONS //
//////////////////////////////////////////////////////
require_once 'app/Mage.php';
umask(0);
Mage::app(0);

///////////////////////////////////
// STORE GIVEN SKU IN A VARIABLE //
///////////////////////////////////
$sku = $_POST['sample-sku'];

//////////////////////////////////////////////
// IF NO SKU IS FOUND THEN REDIRECT US HOME //
//////////////////////////////////////////////
if (!$sku) {
    header("Location: ".Mage::getStoreConfig('web/unsecure/base_url'));
    exit;
}


///////////////////////////////////////////////////////////////////////
// LOAD USERS CURRENT SESSION - THIS FIXES THE SAMPLE SYSTEM FOR 1.8 //
///////////////////////////////////////////////////////////////////////
Mage::getSingleton('core/session', array('name' => 'frontend'));
$session = Mage::getSingleton('customer/session');


////////////////////////////////////////
// GET THE FULL PRODUCT FROM IT'S SKU //
////////////////////////////////////////
$prod = Mage::getModel('catalog/product');
$p    = $prod->loadByAttribute('sku', $sku);


///////////////////////////////////////////////////////////
// LOADS THE CORRECT VARIANT IF A SUPER ATTRIBUTE IS SET //
///////////////////////////////////////////////////////////
if( isset($_POST['super_attribute']) )
{
    $the_product = Mage::getModel('catalog/product_type_configurable')->getProductByAttributes($_POST['super_attribute'], $p);
    if ( is_object($the_product) )
    {
        $p = $the_product;
        $sku = $p->getSku();
    }
}


//////////////////////////////////////////////////
// IF THE PRODUCT IS NOT AN OBJECT THEN GO HOME //
//////////////////////////////////////////////////
if ( !is_object($p) ) {
    header("Location: ".Mage::getStoreConfig('web/unsecure/base_url'));
    exit;
}


/////////////////////////////////////////////////////////////////////
// STORE ORIGINAL PRODUCTS NAME IN CASE WE NEED TO CREATE A SAMPLE //
/////////////////////////////////////////////////////////////////////
$name = $p->getName();


////////////////////////////////////
// SEE IF A SAMPLE ALREADY EXISTS //
////////////////////////////////////
$p = $prod->loadByAttribute('sku', 'S-' . $sku);

if ( is_object($p) ){ $pId = $p->getId(); }
else { $pId = false; }

if ( !$pId )
{

    $product = $prod;
    $product->setSku('S-' . $sku); // PREPEND 'S-' TO SKU TO MAKE IT CLEAR THIS IS A SAMPLE
    $product->setName("Sample of " . $name); // SET THE NAME
    $product->setDescription("Sample of " . $name); // SET THE DESCRIPTION
    $product->setShortDescription($name . " - Sample"); // SET THE SHORT DESCRIPTION
    $product->setPrice(1.00); // SET THE PRICE TO 1.00 - YOU MAY WANT TO CHANGE THIS
    $product->setTypeId('simple'); // WE WANT THIS TO BE A SIMPLE PRODUCT

    $product->setAttributeSetId(0); // THIS NEEDS CHANGING - IN MY CASE IT WAS 4

    $product->setCategoryIds("0"); // CHECK YOUR VALUE(s)
    $product->setWeight(0.000); // SET THE SAMPLES WEIGHT HERE IF YOU HAVE WEIGHT BASED SHIPPING
    $product->setTaxClassId(0); // SET THE TAX GROUP
    $product->setVisibility(1); // nOT VISIBLE INDIVIDUALLY
    $product->setStatus(1); // ENABLE THE PRODUCT
    
    // ASSIGN PRODUCT TO THE DEFAULT WEBSITE
    $product->setWebsiteIds(array(
        Mage::app()->getStore(true)->getWebsite()->getId()
    ));
    
    // GET THE STOCK INFORMATION
    $stockData = $product->getStockData();
    
    // UPDATE STOCK DATA USING NEW DATA
    $stockData['qty']          = 1; // SET STOCK TO 1
    $stockData['is_in_stock']  = 1; // SET PRODUCT TO IN STOCK
    $stockData['manage_stock'] = 0; // DON'T MANAGE THE STOCK OF SAMPLES
    $stockData['max_sale_qty'] = 1; // ALLOW FOR ONLY ONE OF EACH SAMPLE IN CART
    
    // SET THE STOCK INFORMATION
    $product->setStockData($stockData);
    
    // SAVE/CREATE THE PRODUCT
    $product->save();

    // GET THE PRODUCT ID
    $pId = $product->getId();
}

//////////////////////////////
// LOAD THE PRODUCT FROM ID //
//////////////////////////////
$product = Mage::getModel('catalog/product')
                ->setStoreId(Mage::app()->getStore()->getId())
                ->load($pId);

////////////////////////////////////////////////////////////////////
// REDIRECT THE USER TO THE CART WITH THE CORRECTLY GENERATED URL //
////////////////////////////////////////////////////////////////////
header("Location: ".Mage::helper('checkout/cart')->getAddUrl($product).'?product='.$pId.'&qty=1' );
exit;

@YaegerDesign can you please guide how did you added thumbnail image of the product to the cart?

I have tried a lot But i am not able to show product thumbnail image in the cart.Can you please help?

@malikabid Did you manage to resolved your SQL error?