Drop down attributes woocommerce

dropdown-attributes-wc.php

<?php 
// Get the attributes
$attributes = $product->get_attributes();

// Start the loop
$available_variations = $product->get_available_variations();
$product_id = get_the_ID();

if( count($available_variations) > 0 ){

    $output = '<div class="product-variations-dropdown">
        <select id="available-variations" class="" name="available_variations" data-id='. $product_id .'>';

    $output .= '<option value="">'. __('Choose a variation') .'</option>';

    foreach( $available_variations as $variation ){
        $option_value = array();

        foreach( $variation['attributes'] as $attribute => $term_slug ){
            $taxonomy = str_replace( 'attribute_', '', $attribute );
            $attribute_name = get_taxonomy( $taxonomy )->labels->singular_name; // Attribute name
            $term_name = get_term_by( 'slug', $term_slug, $taxonomy )->name; // Attribute value term name

            $option_value[] = $attribute_name . ': '.$term_name;
        }
        $option_value = implode( ' | ', $option_value );

        $output .= '<option value="'.$variation['variation_id'].'">'.$option_value.'</option>';

    }
    $output .= '
        </select>
    </div>';

    echo $output;
} ?>