Source

File: wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php

protected function prepare_item_for_database( $request ) {
		$prepared_user = new stdClass;

		$schema = $this->get_item_schema();

		// Required arguments.
		if ( isset( $request['email'] ) && ! empty( $schema['properties']['email'] ) ) {
			$prepared_user->user_email = $request['email'];
		}

		if ( isset( $request['username'] ) && ! empty( $schema['properties']['username'] ) ) {
			$prepared_user->user_login = $request['username'];
		}

		if ( isset( $request['password'] ) && ! empty( $schema['properties']['password'] ) ) {
			$prepared_user->user_pass = $request['password'];
		}

		// Optional arguments.
		if ( isset( $request['id'] ) ) {
			$prepared_user->ID = absint( $request['id'] );
		}

		if ( isset( $request['name'] ) && ! empty( $schema['properties']['name'] ) ) {
			$prepared_user->display_name = $request['name'];
		}

		if ( isset( $request['first_name'] ) && ! empty( $schema['properties']['first_name'] ) ) {
			$prepared_user->first_name = $request['first_name'];
		}

		if ( isset( $request['last_name'] ) && ! empty( $schema['properties']['last_name'] ) ) {
			$prepared_user->last_name = $request['last_name'];
		}

		if ( isset( $request['nickname'] ) && ! empty( $schema['properties']['nickname'] ) ) {
			$prepared_user->nickname = $request['nickname'];
		}

		if ( isset( $request['slug'] ) && ! empty( $schema['properties']['slug'] ) ) {
			$prepared_user->user_nicename = $request['slug'];
		}

		if ( isset( $request['description'] ) && ! empty( $schema['properties']['description'] ) ) {
			$prepared_user->description = $request['description'];
		}

		if ( isset( $request['url'] ) && ! empty( $schema['properties']['url'] ) ) {
			$prepared_user->user_url = $request['url'];
		}

		if ( isset( $request['locale'] ) && ! empty( $schema['properties']['locale'] ) ) {
			$prepared_user->locale = $request['locale'];
		}

		// Setting roles will be handled outside of this function.
		if ( isset( $request['roles'] ) ) {
			$prepared_user->role = false;
		}

		/**
		 * Filters user data before insertion via the REST API.
		 *
		 * @since 4.7.0
		 *
		 * @param object          $prepared_user User object.
		 * @param WP_REST_Request $request       Request object.
		 */
		return apply_filters( 'rest_pre_insert_user', $prepared_user, $request );
	}