How to override Show field in sonata admin

You can create a custom template for the PostAttributes:

Example:

/* ShowMapper in admin */
$showMapper->add('attributes', null, array(
    'template' => 'YOUR_TEMPLATE.html.twig' // <-- This is the trick
));

In your template, you can extend the base show field (SonataAdminBundle:CRUD:base_show_field.html.twig), and override the field block. The variable named value stores the data in twig.

Example:

YOUR_TEMPLATE.html.twig

{% extends 'SonataAdminBundle:CRUD:base_show_field.html.twig' %}

{% block field %}
    {% for val in value %}
        {{ val.name }} - {{ val.value }} {# I'm just guessing the object properties #}
        <br/>
    {% endfor %}
{% endblock %}