Wordpress - echo implode - php

Question

I've got the following snippet to grab all the terms of the taxonomy available for the post.
$tags = get_the_terms( $post->ID, 'books' );
if( $tags ) : ?>
<div class="listing-tag-list">
<?php foreach( $tags as $tag ) :
$tag_link = esc_url( get_term_link( $tag ) );
$tag_output = '';
$tag_output .= '<a href="' . $tag_link . '" class="listing-tag">';
$tag_output .= '<span class="tag__text">' . $tag->name . '</span></a>';
echo $tag_output;
endforeach; ?>
</div>
<?php endif;
My problem is that currently, the terms show in a row without a space.
How can I separate them with a space and a comma?
I've been trying to use implode and so replace the echo $tag_output; with echo implode( ', ', $tag_output );, but I can't seem to be able to fit it into the current code.
Where am I going wrong?

Answer 1

Why not add it directly in your loop
$tag_output = '';
$tag_output .= '<a href="' . $tag_link . '" class="listing-tag">';
$tag_output .= '<span class="tag__text">' . $tag->name . '</span></a>';
$tag_output .=", ";
echo $tag_output;
And outside the loop,remove the last comma
rtrim($tag_output,', ');

Answer 2

Easy and simple solution:
<?php echo get_the_terms_list( $post_id, 'books', '<div class="listing-tag-list">', ', ', '</div>' );?>
More details on codex
Or this one:
<?php
$tags = get_the_terms( $post->ID, 'books' );
if( ! is_wp_error( $tags ) ){
$links = array();
foreach ( $tags as $tag ) {
$link = get_term_link( $tag, $tag );
$links[] = '<span class="tag__text">' . $tag->name . '</span>';
}
$before = '<div class="listing-tag-list">';
$sep = ', ';
$after = '</div>';
echo $before . join( $sep, $tag_links ) . $after;
}