Displaying values on hook_form
You can try something like this:

 $form['sample'] = array(
     '#type' =&gt; 'item',
     '#markup' =&gt; print_r($sample_values, TRUE),        
 ); 


or simply just

print_r($sample_values);


or install Devel module and use dsm function.

dsm($sample_values);


UPDATE:

Try this:

$form['sample'] = array(
    '#type' =&gt; 'item',
    '#markup' =&gt; print_array_values($sample_values),        
); 


Then declare the function below:

function print_array_values($sample_values){
    $content = '';
    foreach($sample_values as $val){
            $content .= '&lt;div&gt;' . $val . '&lt;/div&gt;';
    }

    return $content;
}