Php--ajax's information:

Php-ajax Introduction:

　　
AJAX is all called "asynchronous JavaScript and XML" (asynchronous JavaScript and xml), Refers to a web development technique that creates an interactive Web application.

Ajax(asynchronous JavaScript + XML) is defined based on web standards (standards-based presentation) The expression of xhtml+css ;

Use the DOM(Document Object Model) for dynamic display and interaction;

Using XML and XSLT for data exchange and related operations;

Using XMLHttpRequest to query and retrieve asynchronous data;

Use JavaScript to bind everything together. In English see the author of Ajax , Jesse James Garrett 's original text.

Similar to DHTML or LAMP,AJAX does not refer to a single technology, but rather organically leverages a range of related technologies. In fact, some AJAX -based "derivation/composition" (derivative/composite) technologies are emerging, such as "Aflax".

　

ajax application:

opera does not support xs Format Object , form ) and send a request to the Web server when the form is submitted. The server receives and processes the form, and then returns a new page. This approach wastes a lot of bandwidth because most of the HTML code in the last two pages is often the same. Because each application interaction requires a request to the server, the response time of the application depends on the response time of the server. This causes the user interface to respond much more slowly than the local application.    Unlike this, soap or some other XML-based web service interface , and the client takes javascript handles responses from . Because the amount of data exchanged between the server and the browser is much reduced, the result is that we can see applications that respond faster. At the same time, a lot of processing can be done on the client machine making the request, so the processing time of the Web server is also reduced.

The advantages of Ajax applications are:

1. Improved user experience through asynchronous mode

2. Optimize the transfer between browser and server, reduce unnecessary data round-trip, reduce the bandwidth consumption

3. The Ajax engine runs on the client side, taking on part of the work that would otherwise have been done by the server, thereby reducing the load on the server under the large user volume.

History:

The technology was applied around the 1998.allow client script to send HTTP requests(XMLHTTP) is the first component of aThe Outlook Web Access Group writes。 The component originally belonged toMicrosoft Exchange Server, and became rapidlypart of Internet Explorer 4.0[3]。 Some observers believe thatOutlook Web AccessIt's the first one to apply.the success of Ajax technologyBusiness applications and become includedOddpost e-mail ProductsMany of the productsleaderHowever, at the beginning of 2005, many events madeAjax is accepted by the public。GoogleAsynchronous communication is used in its well-known interactive applications, such asGoogle discussion groups, Google Maps, Google search suggestions, Gmailsuch asAjaxThis word is made by theajax:a Newapproach to Web applicationsArticle, the rapid spread of the article has improved people's awareness of the use of the technology. In addition, theMozilla/geckoSupport makes the technology more sophisticated and easier to use.

Advantages and Disadvantages:

The biggest advantage of using Ajax is the ability to maintain data without updating the entire page. This allows the Web application to respond more quickly to user actions and avoids sending information that has not changed on the network.

[1] Ajax does not require any browser plugins , but requires the user to allow Javascrip to execute on the browser. Like the DHTML application, AJAX applications have to undergo rigorous testing on many different browsers and platforms. With the maturation of Ajax, a number of libraries that simplify the use of Ajax have been introduced.

[2] Similarly, there is another assistive programming technique that provides alternative functionality for users who do not support JavaScript.

[3] The main criticism of applying Ajax is that it could disrupt the normal behavior of the browser back button

[4]. In the case of dynamically updating the page, the user cannot go back to the previous page state because the browser can only write down the static pages in the history. The difference between a fully read page and a page that has been dynamically modified is very subtle; users often want to click the Back button to cancel their previous operation, but in an AJAX application it is not possible to do so. But developers have come up with ways to solve this problem, most of which is to reproduce changes on the page by creating or using a hidden iframe when the user clicks the Back button to access the history. (for example, when a user clicks back in Google Maps, it searches in a hidden iframe and then reflects the search results on an AJAX element to restore the application state to its current state .) A related view is that using dynamic page updates makes it difficult for users to save a particular state to a collection. The solution for this problem has also occurred, with most of the URL fragment identifiers (often referred to as anchors, parts of the # in the URL) to keep track, allowing the user to return to the specified application state. (many browsers allow JavaScript to dynamically update the anchor point, which allows an AJAX application to update the anchor point while updating the display.)  These solutions also solve a lot of arguments about not supporting back buttons. With Ajax development, network latency-that is, the interval between a user sending a request to a server to make a response-requires careful consideration. Do not give users a clear response

[5], no proper pre-reading data

[6], or improper treatment of XMLHttpRequest

[7], users will feel the delay, which is the user does not want to see, but they do not understand

[8]. A common solution is to use a visual component to tell the user that the system is in the background and is reading data and content.   Some handheld devices (such as mobile phones, PDAs, etc.) are not yet well-supported Ajax; JavaScript ajax engine JavaScript compatibility and debug is a headache;

Ajax non-refresh overload, because the page changes do not refresh the overload so obvious, so easy to bring trouble to users-users are not very clear whether the current data is new or has been updated, the existing solution is: in the relevant location hints, data Update area design is more obvious, the data updated to the user prompt; Support for streaming media is not as good as Flash or Java applet;