<?php
if ( empty( $attributes['data'] ) ) {
    return;
}

$id = 'testimonial-' . ( $attributes['id'] ?? '' );

$buttons = mb_get_block_field( 'btn_group' );
foreach ( $buttons as $button ) {
    $text          = $button['btn_txt'] ?? 'Click me';
    $url           = $button['btn_url'] ?? '#';
    $stacked       = $button['btn_stacked'] ?? false;
    $stacked_style = $stacked ? 'stacked' : '';
    $style         = $button['btn_style'] ?? 'standard';

    echo "<a href='$url' class='$stacked $style'>$text</a>";
}