When should I use GET or POST method? What's the difference between them?

GET Method

GET method is primarily used to request data from a specified resource without altering the data. In other words, GET requests should be idempotent, meaning that repeatedly sending the same GET request should have the same effect as sending it once.

Usage Scenarios:

1. Querying Data: For example, retrieving information from a database or requesting static pages.
2. No Side Effects: GET requests should not cause changes to the server state.

Advantages:

• Can be cached
• Is preserved in browser history
• Can be bookmarked
• Can be reused
• Data is visible in the URL (which can also be a drawback)

Disadvantages:

• Data length is limited (since data is appended to the URL, and URLs have length restrictions)
• Security issues; sensitive data like passwords should not be transmitted via GET because the data appears in the URL

POST Method

POST method is primarily used to submit data to a specified resource, typically causing changes to the server state or data.

Usage Scenarios:

1. Submitting Form Data: Such as user registration or file uploads.
2. Updating Data: For example, updating records in a database.
3. Creating Resources: Creating new records in a database.

Advantages:

• Data is not saved in browser history
• Has no limit on data length
• Is more secure than GET because data is not visible in the URL

Disadvantages:

• Cannot be cached
• Is not preserved in browser history
• Cannot be bookmarked

Summary

In summary, when you need to retrieve information or display data from the server, using GET is appropriate. When you need to send data to the server to change its state or update data, using POST is more appropriate.

Real-world Examples:

• GET: On an e-commerce website, when users browse products, GET method can be used to request product lists or product details because these operations do not change any data on the server.
• POST: When users place orders on the e-commerce website, POST method should be used to submit order information because it involves creating new order records and changing data on the server.