PHP Tutorials. Application Example 2

Tutorial | Application instance Php-push technology to realize refresh function
Server push some time before a very hot "push" technology, but most of the internet is CGI data, and occasionally see a French website there is such an introduction, but the French can not understand, only from his program to understand something, now finishing an example out of everyone to learn. Can be used for chat room data transmission, Web site news updates, and so on all kinds of frequently updated pages.

Previous refreshes were mainly tagged on the page.
　

< META Http-equiv=refresh content= "time; Url=url ">



Or use JavaScript's timeout+reload, but this refresh method depends on the time set, not continuous data transmission and time is not OK. Servers with server push create a permanent connection to the client after a client makes a request, and the server continues to push packets to the server based on the client's request. Those delays that you don't perceive will make you feel that the server's response and your request have reached a level of synchronization.

Let's take a look at the examples and explain.

img.php

< PHP

Set_time_limit (0);

$file = "./1.jpg";

$sep = "Girlskickassitsayssoonatshirt";

if (Ereg (". *msie.*", $HTTP _server_vars["Http_user_agent")) {

If it is IE browser, direct output on the exit, IE does not support oh, I did not try to come out

Header ("Cache-control:no-cache");

Header ("Pragma:no-cache");

Header ("Content-type:image/jpeg");

Header ("Content-size:"). FileSize ($file));

ReadFile ($file);

}else{

Header ("Content-type:multipart/x-mixed-replace; boundary= $sep ");

Here is the key oh, look at the MIME type description



You will understand

Print "--$sep

";

do{

Print "Content-type:image/jpeg

";

ReadFile ($file);

Print "

--$sep

";

Flush ();

$MT = Filemtime ($file);

do{

Sleep (1);

Clearstatcache ();

}while ($MT = = Filemtime ($file));

}while (1);

}

? >



This is a permanently executed page (constantly in the case of the network), constantly outputting the contents of the picture, the following is the page called.
In use you will find a problem: how the picture does not automatically update. This is because the client has not made a request to the server for a period of time, which means that no new content has been entered into the browser for a certain period, and a connection timeout may occur. What solution? You can add an empty signal to the browser in the execution page, similar to the FTP connection, and add a print ("") between Do...while (1) on the page above.

After reading this example, you should know how to deal with the constantly updated content, the key in the Img.php page processing (can be to check the new content and output), call can have IMG, script, frame and so on.