WordPress run php code into the_content loop - php

Question

I'm learning PHP and WordPress development, so I assumed that maybe here I'll find the answer or a tip.
I've restriced the_content based on user role. After the end of the_content I'd like to display button whitch is unique to the specific post. So here is the code which display that:
function displaycontent($content) {
if(is_singular( 'custom_post_type' )) {
$aftercontent = 'I Want To Add Code Here';
$fullcontent = $content . $aftercontent;
} else {
$fullcontent = $content;
}
return $fullcontent;
}
add_filter('the_content', 'displaycontent');
And I'd like to insert code below into the underlined place above:
<?php
$post = $wp_query->post;
$group_id = get_field( 'link_number' , $post->ID );
if( $group_id ) {
echo do_shortcode( '[checkout_button class="button" level="' . $group_id . '" text="Order"]' );
}
?>
How can I do that?

Answer 1

It's probably better to create a custom shortcode for this. If you change how the_content works, it will be global, everywhere.
Note:
This code is completely untested and put together after 5 min of Googling, so if somehting is wrong, feel free to comment and I'll amend it. It should be fairly close and is mostly for explaining the concept instead of a pure copy/paste solution
Register a new shortcode:
add_shortcode('my_awesome_content', 'my_awesome_content_func');
Create the callback function:
Here we've added $atts which will contain our attribute (the post id):
function my_awesome_content_func($atts = [])
{
$postId = $atts['postid'] ?? null;
if ($postId === null) {
// We got no id so let's bail
return null;
}
$post = get_post($postId);
if (!$post) {
// We didn't find any post with the id so again, let's bail
return null;
}
$group_id = get_field( 'link_number' , $post->ID );
$content = $post->content;
if( $group_id ) {
$content .= do_shortcode( '[checkout_button class="button" level="' . $group_id . '" text="Order"]' );
}
return $content;
}
Usage:
Now you should be able to call it like this:
echo do_shortcode('[my_awesome_content postid="' . $post->ID . '"]');

Answer 2

You can just embed you code below in the above filter with some modifications:
function displaycontent($content) {
if (is_singular('custom_post_type')) {
$post_id = get_queried_object_id();
$group_id = get_field('link_number', $post_id);
$aftercontent = '';
if ($group_id)
$aftercontent = do_shortcode('[checkout_button class="button" level="'.$group_id. '" text="Order"]');
$fullcontent = $content.$aftercontent;
} else {
$fullcontent = $content;
}
return $fullcontent;
}
add_filter('the_content', 'displaycontent');

Answer 3

OK, thanks everyone, I Got it! Here is the code if anyone would have same problem:
function displaycontent($content) {
if(is_singular( 'custom_post_type' )) {
$group_id = get_field('link_number');
$aftercontent = do_shortcode( '[checkout_button class="button" level="' . $group_id . '" text="Order"]' );
$fullcontent = $beforecontent . $content . $aftercontent;
} else {
$fullcontent = $content;
}
return $fullcontent;
}
add_filter('the_content', 'displaycontent');