Shortcode to display the post content if it is not empty, otherwise it displays a fallback text.

functions.php

// Shortcode : [post-content-with-fallback-text-if-empty]


function empty_content($str) {
    return trim(str_replace(' ','',strip_tags($str))) == '';
}


function my_sc_content() {
    
    $post = get_post( $id );
    $content = $post->post_content;

    if ( ! $post ) {
        return '';
    }

    if (empty_content($content)) {
        return "La description de ce projet n'est pas encore renseignée.";
    } else {
        return $content;
    }
}

add_shortcode('post-content-with-fallback-text-if-empty','my_sc_content');