[WordPress] Programmatically Add a WooCommerce Variable Product

00-initialize.php

<?php

public function init() {

		add_action(
			'woocommerce_product_after_variable_attributes',
			array( $this, 'variations_field' ),
			10, 3
		);

		add_action(
			'woocommerce_save_product_variation',
			array( $this, 'add_custom_variations_save' ),
			10, 2
		);
	}

01-variations-field.php

<?php

public function variations_field( $loop, $variation_data, $variation ) {

		$description = sanitize_text_field(
			'Enter a information to display to the customer of this product.'
		);

		$args = array(
			'id' 		=> $this->variations,
			'label'		=> sanitize_text_field( 'VHX Package IDs' ),
			'placeholder'	=> '',
			'desc_tip'	=> true,
			'description'	=> $description,
			'value'		=> get_post_meta( $variation->ID, $this->variations, true ),
		);
		woocommerce_wp_text_input( $args );
}

03-saving-information.php

<?php

public function add_custom_variations_save( $post_id ) {

		if ( ! ( isset( $_POST[ $this->variations ] ) || wp_verify_nonce( sanitize_key( $_POST['security'] ), 'woocommerce_save_variations' ) ) ) { // Input var okay.
			return false;
		}

		$variations = sanitize_text_field(
				wp_unslash( $_POST[ $this->variations ] ) // Input var okay.
			)
		);

		update_post_meta(
			$post_id,
			$this->variations,
			esc_attr( $variations )
		);
}