Elementor page builder shortcode issue – unable to include external PHP file when using ob_start and ob_get_clean

I have a weird problem when I try to include my custom wordpress plugin shortcode within elementor. Whenever I use an external php file there is no output.

This code is working fine:

// Shortcode Output function
function vergleichsplugin_output_frontend() 
{

        ob_start();

        echo '<div class="vergleichsplugin"></div>';

        return ob_get_clean();

}


/* Shortcodes */ 
add_shortcode('vergleichsplugin','vergleichsplugin_output_frontend'); 

But this doesn’t produce any output at all (file path is correct):

// Shortcode Output function
function vergleichsplugin_output_frontend() 
{

    ob_start();


    $html = require_once(ABSPATH.'/wp-content/plugins/vergleichsplugin/views/frontend/frontend.php'); 


    $html = $html.ob_get_clean();
    return $html;
}



/* Shortcodes */ 
add_shortcode('vergleichsplugin','vergleichsplugin_output_frontend'); 

content of frontend.php is the same:

echo '<p>Output</p>'; 

>Solution :

Have you tried something like this?

function vergleichsplugin_output_frontend() {
    ob_start();

    include(ABSPATH.'/wp-content/plugins/vergleichsplugin/views/frontend/frontend.php'); 

    return ob_get_clean();
}
add_shortcode('vergleichsplugin','vergleichsplugin_output_frontend');