Final Class Yiisoft\View\PhpTemplateRenderer

                public function render(ViewInterface $view, string $template, array $parameters): string
{
    $renderer = function (): void {
        /** @psalm-suppress MixedArgument, PossiblyFalseArgument */
        extract(func_get_arg(1), EXTR_OVERWRITE);
        /** @psalm-suppress UnresolvableInclude */
        require func_get_arg(0);
    };
    $obInitialLevel = ob_get_level();
    ob_start();
    ob_implicit_flush(false);
    try {
        /** @psalm-suppress PossiblyInvalidFunctionCall,PossiblyNullFunctionCall */
        $renderer->bindTo($view)($template, $parameters);
        /**
         * @var string We assume that in this case active output buffer is always existed, so `ob_get_clean()`
         * returns a string.
         */
        return ob_get_clean();
    } catch (Throwable $e) {
        while (ob_get_level() > $obInitialLevel) {
            ob_end_clean();
        }
        throw $e;
    }
}