In this tutorial, we'll develop a secure poll and voting system using PHP and MySQL. This system will allow you to interact with your audience and display a collection of polls. You'll learn to create polls, implement a voting system, delete polls, and display the list of published polls., React-Query’s useQuery hook provides several powerful options that can help you build flexible and efficient data-fetching solutions in your React applications. Whether you need to poll an API at a regular interval, fetch data in the background, or transform the data before it’s returned to the component, options like refetchInterval , We make use of Placeholder in forms, to show data related to the entity. For example let's say we have an EditUser page and form. We are using Placeholder as an example while viewing this page, to show some interesting live updating status about some thing based on this user., Placeholder Query Data. Initial Query Data. Prefetching. Mutations. Query Invalidation. Invalidation from Mutations. Updates from Mutation Responses. Optimistic Updates. Query Cancellation. Scroll Restoration. Auto Refetching / Polling / Realtime. Window Refocus Refetching. Optimistic Updates., If set, this value will be used as the placeholder data for this particular query observer while the query is still in the loading data and no initialData has been provided. placeholderData is not persisted to the cache, Placeholder data allows a query to behave as if it already has data, similar to the initialData option, but the data is not persisted to the cache. This comes in handy for situations where you have enough partial (or fake) data to render the query successfully while the actual data is fetched in the background..