call blog primary category

Hi,

I would like to call the primary category of my blog posts through Rankmath.

Previously with Yoast, I used this code to do it:

// Add Shortcode
function get_yoast_primary_cat() {

Fill in your custom taxonomy here
$yourTaxonomy = ‘category’;

// SHOW YOAST PRIMARY CATEGORY, OR FIRST CATEGORY
$category = get_the_terms( $postId, $yourTaxonomy );
$useCatLink = true;

// If post has a category assigned.
if ($category){
$category_display = ”;
$category_link = ”;
if ( class_exists(‘WPSEO_Primary_Term’) )
{

// Show the post’s ‘Primary’ category, if this Yoast feature is available, & one is set
$wpseo_primary_term = new WPSEO_Primary_Term( ‘event_cat’, get_the_id() );
$wpseo_primary_term = $wpseo_primary_term->get_primary_term();
$term = get_term( $wpseo_primary_term );
if (is_wp_error($term)) {

// Default to first category (not Yoast) if an error is returned
$category_display = $category[0]->name;
$category_link = get_bloginfo(‘url’) . ‘/’ . ‘event-category/’ . $term->slug;
} else {

// Yoast Primary category
$category_display = $term->name;
$category_link = get_term_link( $term->term_id );
}
}
else {

// Default, display the first category in WP’s list of assigned categories
$category_display = $category[0]->name;
$category_link = get_term_link( $category[0]->term_id );
}

// Display category
if ( !empty($category_display) ){
if ( $useCatLink == true && !empty($category_link) ){
echo ‘<span class=”post-category”>’;
echo ‘‘.$category_display.’‘;
echo ‘</span>’;
} else {
echo ‘<span class=”post-category”>’.$category_display.'</span>’;
}
}

}

}
add_shortcode( ‘yoast-primary-category’, ‘get_yoast_primary_cat’ );