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Starting with HTML 4.0, forms can also submit data in multipart/form-data as defined in RFC 2388 (See also RFC 1867 for an earlier experimental version defined as an extension to HTML 2.0 and mentioned in HTML 3.2). The special case of a POST to the same page that the form belongs to is known as a postback.
A query string is a part of a uniform resource locator that assigns values to specified parameters.A query string commonly includes fields added to a base URL by a Web browser or other client application, for example as part of an HTML document, choosing the appearance of a page, or jumping to positions in multimedia content.
The target PHP file then accesses the data passed by the form through PHP's $_POST or $_GET variables, depending on the value of the method attribute used in the form. Here is a basic form handler PHP script that will display the contents of the first_name input field on the page: form.html
Diagram of a double POST problem encountered in user agents. Diagram of the double POST problem above being solved by PRG. Post/Redirect/Get (PRG) is a web development design pattern that lets the page shown after a form submission be reloaded, shared, or bookmarked without ill effects, such as submitting the form another time.
GET The GET method requests that the target resource transfer a representation of its state. GET requests should only retrieve data and should have no other effect. (This is also true of some other HTTP methods.) [1] For retrieving resources without making changes, GET is preferred over POST, as they can be addressed through a URL.
The webpage can be modified by JavaScript to dynamically display (and allow the user to interact with) the new information. The built-in XMLHttpRequest object is used to execute Ajax on webpages, allowing websites to load content onto the screen without refreshing the page.
This "wrapped payload" is then interpreted by the browser. In this way, a function that is already defined in the JavaScript environment can manipulate the JSON data. A typical JSONP request and response are shown below. The function call to parseResponse() is the "P" of JSONP—the "padding" or "prefix" around the pure JSON. [4]
XMLHttpRequest (XHR) is an API in the form of a JavaScript object whose methods transmit HTTP requests from a web browser to a web server. [1] The methods allow a browser-based application to send requests to the server after page loading is complete, and receive information back. [2] XMLHttpRequest is a component of Ajax programming.