WP_REST_Posts_Controller::create_item( WP_REST_Request $request )

	public function create_item( $request ) {
		if ( ! empty( $request['id'] ) ) {
			return new WP_Error( 'rest_post_exists', __( 'Cannot create existing post.' ), array( 'status' => 400 ) );
		}

		$prepared_post = $this->prepare_item_for_database( $request );

		if ( is_wp_error( $prepared_post ) ) {
			return $prepared_post;
		}

		$prepared_post->post_type = $this->post_type;

		$post_id = wp_insert_post( wp_slash( (array) $prepared_post ), true );

		if ( is_wp_error( $post_id ) ) {

			if ( 'db_insert_error' === $post_id->get_error_code() ) {
				$post_id->add_data( array( 'status' => 500 ) );
			} else {
				$post_id->add_data( array( 'status' => 400 ) );
			}

			return $post_id;
		}

		$post = get_post( $post_id );

		/**
		 * Fires after a single post is created or updated via the REST API.
		 *
		 * The dynamic portion of the hook name, `$this->post_type`, refers to the post type slug.
		 *
		 * @since WP-4.7.0
		 *
		 * @param WP_Post         $post     Inserted or updated post object.
		 * @param WP_REST_Request $request  Request object.
		 * @param bool            $creating True when creating a post, false when updating.
		 */
		do_action( "rest_insert_{$this->post_type}", $post, $request, true );

		$schema = $this->get_item_schema();

		if ( ! empty( $schema['properties']['sticky'] ) ) {
			if ( ! empty( $request['sticky'] ) ) {
				stick_post( $post_id );
			} else {
				unstick_post( $post_id );
			}
		}

		if ( ! empty( $schema['properties']['featured_media'] ) && isset( $request['featured_media'] ) ) {
			$this->handle_featured_media( $request['featured_media'], $post_id );
		}

		if ( ! empty( $schema['properties']['format'] ) && ! empty( $request['format'] ) ) {
			set_post_format( $post, $request['format'] );
		}

		if ( ! empty( $schema['properties']['template'] ) && isset( $request['template'] ) ) {
			$this->handle_template( $request['template'], $post_id, true );
		}

		$terms_update = $this->handle_terms( $post_id, $request );

		if ( is_wp_error( $terms_update ) ) {
			return $terms_update;
		}

		if ( ! empty( $schema['properties']['meta'] ) && isset( $request['meta'] ) ) {
			$meta_update = $this->meta->update_value( $request['meta'], $post_id );

			if ( is_wp_error( $meta_update ) ) {
				return $meta_update;
			}
		}

		$post = get_post( $post_id );
		$fields_update = $this->update_additional_fields_for_object( $post, $request );

		if ( is_wp_error( $fields_update ) ) {
			return $fields_update;
		}

		$request->set_param( 'context', 'edit' );

		$response = $this->prepare_item_for_response( $post, $request );
		$response = rest_ensure_response( $response );

		$response->set_status( 201 );
		$response->header( 'Location', rest_url( sprintf( '%s/%s/%d', $this->namespace, $this->rest_base, $post_id ) ) );

		return $response;
	}