Getting the post all categories with comma separated - php

Question

I am trying to get the categories in a post like this example if the post is added in cate1, cate2, and cate3 then the post-show 3 categories like cate1, cate2, cate3 if the post is posted in one category then just show the cate1 without a comma. But my code $slug = $category->slug; only shows one category in the post. here is my full code.
<?php
$mi_args = array(
'post_status' => 'publish',
'posts_per_page' => '99999',
'post_type' => 'blog'
);
$mi_query = new WP_Query($mi_args);
if($mi_query->have_posts()):
while ($mi_query->have_posts()): $mi_query->the_post();
$portfolio_url = get_post_meta( get_the_ID(), 'portfolio_url_portfolio-url', true );
$hover_color = get_post_meta( get_the_ID(), 'hove_color_hover-color', true );
// Getting the category slug
$work_category = get_the_terms( get_the_ID(), 'blog_categories' );
foreach ($work_category as $category)
{
$slug = $category->slug;
?>
<div class="portfolio-item <?php echo $slug; ?>" data-category="<?php echo $slug; ?>">
<?php
}
?>
<?php endwhile; endif; wp_reset_postdata(); ?>

Answer 1

If I understand your question, you want to take an array of category slugs, and put them as a comma separated list?
If that's right, then you want to push your slugs to an array, and then implode it to a list.
<?php
$mi_args = array(
'post_status' => 'publish',
'posts_per_page' => -1,
'post_type' => 'blog',
);
$mi_query = new WP_Query( $mi_args );
if ( $mi_query->have_posts() ) :
while ( $mi_query->have_posts() ) :
$mi_query->the_post();
$portfolio_url = get_post_meta( get_the_ID(), 'portfolio_url_portfolio-url', true );
$hover_color = get_post_meta( get_the_ID(), 'hove_color_hover-color', true );
// Getting the category slug.
$work_category = get_the_terms( get_the_ID(), 'blog_categories' );
$slug = array();
foreach ( $work_category as $category ) {
$slug[] = $category->slug;
}
$slug_list = implode( ',', $slug );
?>
<div class="portfolio-item <?php echo esc_attr( $slug_list ); ?>" data-category="<?php echoesc_attr( $slug_list ); ?>">
<?php
endwhile;
endif;
wp_reset_postdata();
?>