Wordpress after content Hook & external template part

Question

I am trying to use this method to include a template part (HTML Code) rather than using some plain text. When I use text, it shows correctly below the content with the the_content filter. However, If I try to get_template_part, the content shows at the top of the Wordpress post rather than below the content.

Is there a better way to include/get template parts hooked to the before/after of single content in Wordpress?

Here is the code I am trying with the filter:

function educadme_book_fields_content_hook( $content ) {    
if( is_singular('books') ) {            
$beforecontent = '';
$aftercontent = get_template_part( 'parts/book', 'fields' );
$fullcontent = $beforecontent . $content . $aftercontent;
return $fullcontent;
}

Also tried:

$content .= get_template_part( 'parts/book', 'fields' );
return $content;

Still getting the same issue as all content of the get_template_part are shown above even the title, not just the_content. Thanks!

Answer 1

Be aware that a mix of return and echo from a function will change text positioning.

If you take this simple example :

function test(){
    $the_test = 'test return';
    echo 'test echo';
    return $the_test;
}

echo test();

Whatever the place of the echoed line, this line will be always print before echo test(); because echo is called before the return $the_test;

You need to play with get_template_part and/or template_redirect action to display your content like you want.

Hope your understand what I mean and the relation with your issue ;-)

Answer 2

Ok since get_template_part and require couldn't be used since they echoed the content above the content and not below (Thanks @benoti), I decided to use a different approach:

ob_start(); ?>
<? global $post; ?>

Long HTML Content with some PHP variables inside to load all the custom fields & style I wanted instead of using an external file which I prepared before.

<?php
$book_fields = ob_get_clean();      
$fullcontent = $content . $book_fields;
return $fullcontent;