How to get current selected variable product specific data in WooCommerce

I want to access the selected product variation Weight value in php. I tried below code its getting last value of attribute, not selected.

foreach($product->get_available_variations() as $values){
    $weight = $values['attributes']["attribute_weight"];
}

Answer

The selected variation properties can only be accessed via Javascript as it’s a client side live event… Here below is an example, that will display the selected variation custom attribute “attribute_weight” term slug for the variable product, below add to cart button:

add_action( 'woocommerce_after_add_to_cart_form', 'display_selected_variation_data');
function display_selected_variation_data() {
    global $product;

    ## For variable products (and their variations)
    if(  $product->is_type('variable') ) {

        // Here below set your custom attribute name
        $attribute_name = 'attribute_weight'; // Or "attribute_pa_weight" for non custom attributes
        ?>
        <p class="custom-<?php echo $attribute_name; ?>" style="border:solid 1px black; text-align:center"></div>
        <script type="text/javascript">
        jQuery( function($){
            // On select variation event
            $('form.variations_form').on('show_variation', function( event, data ){
                var attrValue = data.attributes.<?php echo $attribute_name; ?>;

                $( 'p.custom-<?php echo $attribute_name; ?>' ).html( data.attributes.<?php echo $attribute_name; ?> );;

                // For testing (displayed on the browser's console)
                console.log( 'Variation Id: ' + data.variation_id + ' | Attribute value: ' + attrValue );
            });
            // On unselect variation event
            $('form.variations_form').on('hide_variation', function(){
                $( 'p.custom-<?php echo $attribute_name; ?>' ).html( '<em>no value</em>' );
            });
        });
        </script><?php
    }
}

Code goes in functions.php file of the active child theme (or active theme). Tested and works.

Related: Get currently selected variation id from Woocommerce variable product