Astra Portfolio - URL rewrite with https://example.com/%astra-portfolio-categories%/portfolio-title

post-type-rewrite.php

<?php
/**
 * Add rewrite rule.
 *
 * @since 1.0.0
 *
 * @param array $rules Existing rewrite rules
 * @return array
 */
if( ! function_exists( 'prefix_add_rewrite_rules' ) ) {
	function prefix_add_rewrite_rules( $rules ) {

		// Add new rule.
		$new = array(
			'astra-portfolio/([^/]+)/(.+)/?$' => 'index.php?astra-portfolio=$matches[2]'
		);

		return array_merge( $new, $rules );
	}
	add_filter( 'rewrite_rules_array', 'prefix_add_rewrite_rules' );
}

/**
 * Handle the '%astra-portfolio-categories%' URL placeholder
 *
 * @since 1.0.0
 *
 * @param array $link New link.
 * @return array
 */
if( ! function_exists( 'prefix_replace_placeholders' ) ) {
	function prefix_replace_placeholders( $link, $post ) {
		if ( $post->post_type == 'astra-portfolio' ) {

			$categories = get_the_terms( $post->ID, 'astra-portfolio-categories' );
			if ( $categories ) {
				$link = str_replace( '%astra-portfolio-categories%', current( $categories )->slug, $link );
			}
		}

		return $link;
	}

	add_filter( 'post_type_link', 'prefix_replace_placeholders', 10, 2 );
}

/**
 * Handle the '%astra-portfolio-categories%' URL placeholder
 *
 * @since 1.0.0
 *
 * @param array $rules Existing rewrite rules
 * @return array
 */
if( ! function_exists( 'prefix_add_post_type_rewrite_slug' ) ) {
	function prefix_add_post_type_rewrite_slug( $args ) {
		$args['rewrite'] = array(
			'slug' => 'astra-portfolio/%astra-portfolio-categories%',
			'with_front' => true
		);
		return $args;
	}
	add_filter( 'astra_portfolio_post_type_args', 'prefix_add_post_type_rewrite_slug' );
}