Update Post Type Labels

functions.php

<?php

function refsites_update_labels() {

	// Only run this function on the front end
	if ( is_admin() ) {
		return;
	}

	$post_types = array( 'post', 'sr_playlist' );

	$new_labels = array(
		'post' => array(
			'name'          => 'Articles',   // New plural label
			'singular_name' => 'Article', // New singular label
		),
		'sr_playlist' => array(
			'name'          => 'Podcasts',   // New plural label
			'singular_name' => 'Podcast', // New singular label
		),
	);

	foreach( $post_types as $post_type ) {
		// Get the existing post type object
		$post_type_object = get_post_type_object( $post_type );

		if ( ! $post_type_object ) {
			return;
		}

		// Retrieve the existing arguments
		$args = (array) $post_type_object;

		// Modify the labels while keeping all other arguments
		$args['label']  = $new_labels[ $post_type ]['name'];
		$args['labels'] = array_merge( (array) $post_type_object->labels, $new_labels[ $post_type ] );

		// Re-register the post type with updated labels and original arguments
		register_post_type( $post_type, $args );
	}

}
add_action( 'init', 'refsites_update_labels', 500 );