[WordPress] Templating and Conditional Logic with OOP

00-template-example.php

<div class="wrap">
    <!-- Snipping out irrelevant code in this file -->
    <form id="yhd-upload-new-item-settings">
        <?php if (!$this->hasSecondaryPlugin()) { ?>
            <?php include_once 'partials/error-inactive-plugin.php'; ?>
        <?php } else { ?>
            <h2>Secondary Plugin Settings</h2>
            <p class="description">The Secondary Plugin is installed and active.</p>
            <form method="post" action="<?php echo esc_html(admin_url('admin-post.php')); ?>">
                <label for="acme-secondary-plugin">
                    <input type="checkbox" name="acme-secondary-plugin" value="true"/>
                    Would you like to automatically use the secondary plugin?
                </label>
                <!-- Snipping out irrelevant code in this file -->
            </form>
        <?php } ?>
    </div>
</div>

01-error-inactive-plugin.php

<?php
/**
 * This is the partial displayed when the Secondary Plugin is not active.
 */
?>
<div id="inactive-importer-message" class="error notice is-dismissible">
    <p>[The message you want to display here.]</p>
    <button type="button" class="notice-dismiss">
        <span class="screen-reader-text">Dismiss this notice.</span>
    </button>
</div><!-- #inactive-importer-message -->

02-hasSecondaryPlugin.php

<?php

/**
 * Determines if the Secondary Importer is is activated.
 *
 * @return bool True if the the pklugin is active; false, otherwise.
 */
private function hasSecondaryPlugin()
{
    return in_array(
        'secondary-plugin/secondary-plugin.php',
        get_option('active_plugins')
    );
}