Plugin_Upgrader::check_package( string $source ): string|WP_Error

462	public function check_package( $source ) {463		global $wp_filesystem;464 465		$wp_version            = wp_get_wp_version();466		$this->new_plugin_data = array();467 468		if ( is_wp_error( $source ) ) {469			return $source;470		}471 472		$working_directory = str_replace( $wp_filesystem->wp_content_dir(), trailingslashit( WP_CONTENT_DIR ), $source );473		if ( ! is_dir( $working_directory ) ) { // Confidence check, if the above fails, let's not prevent installation.474			return $source;475		}476 477		// Check that the folder contains at least 1 valid plugin.478		$files = glob( $working_directory . '*.php' );479		if ( $files ) {480			foreach ( $files as $file ) {481				$info = get_plugin_data( $file, false, false );482				if ( ! empty( $info['Name'] ) ) {483					$this->new_plugin_data = $info;484					break;485				}486			}487		}488 489		if ( empty( $this->new_plugin_data ) ) {490			return new WP_Error( 'incompatible_archive_no_plugins', $this->strings['incompatible_archive'], __( 'No valid plugins were found.' ) );491		}492 493		$requires_php = isset( $info['RequiresPHP'] ) ? $info['RequiresPHP'] : null;494		$requires_wp  = isset( $info['RequiresWP'] ) ? $info['RequiresWP'] : null;495 496		if ( ! is_php_version_compatible( $requires_php ) ) {497			$error = sprintf(498				/* translators: 1: Current PHP version, 2: Version required by the uploaded plugin. */499				__( 'The PHP version on your server is %1$s, however the uploaded plugin requires %2$s.' ),500				PHP_VERSION,501				$requires_php502			);503 504			return new WP_Error( 'incompatible_php_required_version', $this->strings['incompatible_archive'], $error );505		}506 507		if ( ! is_wp_version_compatible( $requires_wp ) ) {508			$error = sprintf(509				/* translators: 1: Current WordPress version, 2: Version required by the uploaded plugin. */510				__( 'Your WordPress version is %1$s, however the uploaded plugin requires %2$s.' ),511				$wp_version,512				$requires_wp513			);514 515			return new WP_Error( 'incompatible_wp_required_version', $this->strings['incompatible_archive'], $error );516		}517 518		return $source;519	}