Ajax long Polling (Longpoll) _php tutorial based on jquery and PHP

The traditional Ajax polling method, the customer service side at the user-defined time interval to the server to query the latest data. This kind of pull data takes a short time interval to ensure the accuracy of the data, but too short a time interval client sends multiple requests to the server in a short period of time.

Reverse Ajax, which is called long polling or comet. The server and customer service need to maintain a long-time request, which allows the server to return messages to the client when there is data.

Xhtml

 
  
  

  
   
   
< Div  id="msg">  div >  
  
   
   
< input  id="btn"type="button"  value="Test"/> 
 
  
  

Jquery

This uses Ajax to request the data.php page to get the value of ' success ', requesting a time of 80 seconds. In these 80 seconds, if no return from the server ' success ' is kept in a connected state until there is a data return or ' success ' value of 0 to close the connection. The next request continues after the connection is closed.

 
 

  
  

  
$ (function() {
  
  

  
$ ("#btn"). Bind ("click", {btn:$ ("#btn")},  function(evdata) {
  
  

  
$.ajax ({
  
  

  
Type: "POST" , 
  
  

  
DataType: "JSON" , 
  
  

  
URL: "data.php" , 
  
  

  
timeout:80000, //ajax Request Time-out time 80 seconds  
  
  

  
data:{time:"i"}, ///40 seconds after data is returned regardless of the result server  
  
  

  
Success: function (data,textstatus) {
  
  

  
 //Get data from the server, display the data and continue querying  
  
  

  
 if (data.success=="1") {
  
  

  
$ ("#msg"). Append ("
[With Data] "+data.text); 
  
  

  
Evdata.data.btn.click ();
  
  

  
}
  
  

  
 //did not get data from the server, continue to query  
  
  

  
 if (data.success=="0") {
  
  

  
$ ("#msg"). Append ("
[No data] "); 
  
  

  
Evdata.data.btn.click ();
  
  

  
}
  
  

  
},
  
  

  
 //ajax Request timed out, continue querying  
  
  

  
Error: function (xmlhttprequest,textstatus,errorthrown) {
  
  

  
 if (textstatus=="Timeout") {
  
  

  
$ ("#msg"). Append ("
[Timeout] "); 
  
  

  
Evdata.data.btn.click ();
  
  

  
}
  
  

  
}
  
  

  
 
  
  

  
});
  
  

  
});
  
  

  
 
  
  

  
});
 
 

Php

Here is the infinite loop, the end condition of the loop is to get the return result to return the JSON data.

and accept the $_post[' time ' parameter to limit the cycle timeout and avoid excessive waste of resources. (browser close will not send a message to the server, use may have been looped down)

 
 

  
  

  
if (emptyempty($_post[' time '])) Exit (); 
  
  

  
set_time_limit (0); //Unlimited Request time-out  
  
  

  
$i = 0; 
  
  

  
 while (true) {
  
  

  
 //sleep (1);  
  
  

  
Usleep (500000); //0.5 sec  
  
  

  
 $i ++; 
  
  

  
 
  
  

  
 //If the data is available, return the data to the customer service immediately and end the request.  
  
  

  
 $rand =rand (1,999); 
  
  

  
 if ($rand<=15) {
  
  

  
 $arr = Array (' success '= '1',' name '='xiaocai '  ,' text '=$rand); 
  
  

  
 Echo Json_encode ($arr); 
  
  

  
 Exit (); 
  
  

  
}
  
  

  
 
  
  

  
 //server ($_post[' time ']*0.5) seconds to tell the customer service end no data  
  
  

  
 if ($i= =$_post[' time ']) {
  
  

  
 $arr = Array (' success '= '0',' name '= = ' Xiaocai ' , ' text ' = $rand ); 
  
  

  
 Echo Json_encode ($arr); 
  
  

  
 Exit (); 
  
  

  
}
  
  

  
}
 
 

Run effect: In the graph can see the request time of no data reached 40S, in the request of 40S to obtain the data request closes.

http://www.bkjia.com/PHPjc/445814.html www.bkjia.com true http://www.bkjia.com/PHPjc/445814.html techarticle The traditional Ajax polling method, the customer service side at the user-defined time interval to the server to query the latest data. This kind of pull data takes a short time interval to guarantee the data ...

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