have post get the category code example

Example 1: wordpress get post category name

<?php
$categories = get_the_category();
 
if ( ! empty( $categories ) ) {
    echo esc_html( $categories[0]->name ); // Show first item of category  
}
?>

Example 2: wordpress display post categories

<?php the_terms( $post->ID, 'topics', 'Topics: ', ', ', ' ' ); ?>