WordPress convert post post_type to cpt based on post category

wordpress-convert-post-to-cpt.php

<?php

/**
 * Implements `dsca` command.
 */
class DSCA_Helpers {

	/**
	 * Change a custom post type.
	 *
	 * ## OPTIONS
	 *
	 * <post_type>
	 * : The custom post type to change.
	 *
	 * [--to=<new post type>]
	 * : The post type slug to change to
	 *
	 * ## EXAMPLES
	 *
	 *     wp dscs changecpt books --to=posts
	 *
	 * @when after_wp_load
	 */
	function changecpt( $args, $assoc_args ) {
		list( $post_type ) = $args;
		$to = $assoc_args['to'];

		$myquery = new WP_Query([
			'post_type'      => $post_type,
			'post_status'    => 'any',
			'posts_per_page' => '-1'
			// any additional tax or post_meta query here.
		]);

		foreach ( $myquery->posts as $apost ) {
			wp_update_post( [
				'ID' => $apost->ID,
				'post_type' => $to // boom!
			] );
			WP_CLI::success( $apost->post_title . " - is now " . $to );
		}
	}
}

WP_CLI::add_command( 'dsca', 'DSCA_Helpers' );

// run with `wp dscs changecpt books --to=posts`