Concurrent implementation of curl function in PHP reduces backend access time

The content of this article is to share with you the curl function concurrency implementation in PHP to reduce back-end access time. It has a certain reference value. Friends in need can refer to it

First of all, let’s understand PHP curl multi-threaded function in:

# curl_multi_add_handle
# curl_multi_close
# curl_multi_exec
# curl_multi_getcontent
# curl_multi_info_read
# curl_multi_init
# curl_multi_remove_handle
# curl_multi_select

Generally speaking, when you think of using these functions, the purpose should obviously be to request multiple URLs at the same time, rather than requesting them one by one. Otherwise, it is better to loop and adjust curl_exec yourself.

The steps are summarized as follows:

The first step: Call curl_multi_init
The second step: Call curl_multi_add_handle in a loop
It should be noted in this step that the second parameter of curl_multi_add_handle is given by Subhandle from curl_init.
Step 3: Continuously call curl_multi_exec
Step 4: Cyclically call curl_multi_getcontent to obtain the results as needed
Step 5: Call curl_multi_remove_handle, and call curl_close for each word handle
Step 6: Call curl_multi_close

Here is a simple example found online. The author calls it a dirty example (I will explain why dirty later):

/*
Here's a quick and dirty example for curl-multi from PHP, tested on PHP 5.0.0RC1 CLI / FreeBSD 5.2.1
*/
$connomains = array(
"http://www.cnn.com/",
"http://www.canada.com/",
"http://www.yahoo.com/"
);
$mh = curl_multi_init();
foreach ($connomains as $i => $url) {
     $conn[$i]=curl_init($url);
      curl_setopt($conn[$i],CURLOPT_RETURNTRANSFER,1);
      curl_multi_add_handle ($mh,$conn[$i]);
}
do { $n=curl_multi_exec($mh,$active); } while ($active);
foreach ($connomains as $i => $url) {
      $res[$i]=curl_multi_getcontent($conn[$i]);
      curl_close($conn[$i]);
}
print_r($res);

The whole usage process is almost like this , however, this simple code has a fatal weakness, that is, the section of the do loop is an infinite loop during the entire url request, which can easily cause the CPU to occupy 100%.

Now let's improve it. Here we need to use a function curl_multi_select that has almost no documentation. Although C's curl library has instructions for select, the interface and usage in PHP are indeed different from those in C. .

Change the do section above to the following:
            

 do {
                        $mrc = curl_multi_exec($mh,$active);
                } while ($mrc == CURLM_CALL_MULTI_PERFORM);
                while ($active and $mrc == CURLM_OK) {
                        if (curl_multi_select($mh) != -1) {
                                do {
                                        $mrc = curl_multi_exec($mh, $active);
                                } while ($mrc == CURLM_CALL_MULTI_PERFORM);
                        }
                }

Because $active has to wait until all url data is received before it becomes false, so the return value of curl_multi_exec is used here Determine whether there is still data. When there is data, curl_multi_exec will be called continuously. If there is no data for the time being, it will enter the select stage. Once new data comes, it can be awakened to continue execution. The advantage here is that there is no unnecessary consumption of CPU.

In addition: There are some details that may sometimes be encountered:

Control the timeout of each request, do it through curl_setopt before curl_multi_add_handle:
curl_setopt($ch , CURLOPT_TIMEOUT, $timeout);

To determine whether there is a timeout or other errors, use curl_error($conn[$i]);

before curl_multi_getcontent: curl_error($conn[$i]);

1. $requests = array('http://www.baidu.com', 'http://www.google.com');  
   $main    = curl_multi_init();  
   $results = array();  
   $errors  = array();  
   $info = array();  
   $count = count($requests);  
   for($i = 0; $i < $count; $i++)   
   {    
   $handles[$i] = curl_init($requests[$i]);    
   var_dump($requests[$i]);    
   curl_setopt($handles[$i], CURLOPT_URL, $requests[$i]);    
   curl_setopt($handles[$i], CURLOPT_RETURNTRANSFER, 1);    
   curl_multi_add_handle($main, $handles[$i]);  
   }  
   $running = 0;   
   do {    
   curl_multi_exec($main, $running);  
   }   
   while($running > 0);   
   for($i = 0; $i < $count; $i++)  
   {  $results[] = curl_multi_getcontent($handles[$i]);    
   $errors[]  = curl_error($handles[$i]);    
   $info[]    = curl_getinfo($handles[$i]);    
   curl_multi_remove_handle($main, $handles[$i]);  
   }  
   curl_multi_close($main);  
   var_dump($results);  
   var_dump($errors);  
   var_dump($info);

   Copy after login

前言：在我们平时的程序中难免出现同时访问几个接口的情况，平时我们用curl进行访问的时候，一般都是单个、顺序访问，假如有3个接口，每个接口耗时500毫秒那么我们三个接口就要花费1500毫秒了，这个问题太头疼了严重影响了页面访问速度，有没有可能并发访问来提高速度呢？今天就简单的说一下，利用curl并发来提高页面访问速度，希望大家多指导。1、老的curl访问方式以及耗时统计

1. <?php function curl_fetch($url, $timeout=3){       
   $ch = curl_init();       
   curl_setopt($ch, CURLOPT_URL, $url);       
   curl_setopt($ch, CURLOPT_TIMEOUT, $timeout);       
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);       
   $data = curl_exec($ch);       
   $errno = curl_errno($ch);       
   if ($errno>0) {           
   $data = false;       
   }       
   curl_close($ch);       
   return $data;   
   }   
   function microtime_float()   
   {      
   list($usec, $sec) = explode(" ", microtime());      
   return ((float)$usec + (float)$sec);   
   }   
   $url_arr=array(        
   "taobao"=>"http://www.taobao.com",        
   "sohu"=>"http://www.sohu.com",        
   "sina"=>"http://www.sina.com.cn",        
   );    
   $time_start = microtime_float();    
   $data=array();    
   foreach ($url_arr as $key=>$val)    
   {        
   $data[$key]=curl_fetch($val);    
   }    
   $time_end = microtime_float();    
   $time = $time_end - $time_start;    
   echo "耗时:{$time}";   
   ?>

   Copy after login

耗时:0.614秒
2、curl并发访问方式以及耗时统计

1. <?php   
   function curl_multi_fetch($urlarr=array()){       
   $result=$res=$ch=array();       
   $nch = 0;       
   $mh = curl_multi_init();       
   foreach ($urlarr as $nk => $url) {           
   $timeout=2;           
   $ch[$nch] = curl_init();           
   curl_setopt_array($ch[$nch], array(           
   CURLOPT_URL => $url,           
   CURLOPT_HEADER => false,           
   CURLOPT_RETURNTRANSFER => true,           
   CURLOPT_TIMEOUT => $timeout,           
   ));           
   curl_multi_add_handle($mh, $ch[$nch]);           
   ++$nch;     }       
   /* wait for performing request */      
   do {           
   $mrc = curl_multi_exec($mh, $running);       
   } while (CURLM_CALL_MULTI_PERFORM == $mrc);         
   while ($running && $mrc == CURLM_OK) {           
   // wait for network           
   if (curl_multi_select($mh, 0.5) > -1) {               
   // pull in new data;               
   do {                   
   $mrc = curl_multi_exec($mh, $running);               
   } while (CURLM_CALL_MULTI_PERFORM == $mrc);           
   }       
   }         
   if ($mrc != CURLM_OK) {           
   error_log("CURL Data Error");       
   }         
   /* get data */      
   $nch = 0;       
   foreach ($urlarr as $moudle=>$node) {           
   if (($err = curl_error($ch[$nch])) == &#39;&#39;) {               
   $res[$nch]=curl_multi_getcontent($ch[$nch]);             $result[$moudle]=$res[$nch];         }           
   else          
   {               
   error_log("curl error");           
   }           
   curl_multi_remove_handle($mh,$ch[$nch]);           
   curl_close($ch[$nch]);           
   ++$nch;       
   }       
   curl_multi_close($mh);       
   return  $result;   
   }   
   $url_arr=array(        
   "taobao"=>"http://www.taobao.com",        
   "sohu"=>"http://www.sohu.com",        
   "sina"=>"http://www.sina.com.cn",        
   );   
   function microtime_float()   
   {      
   list($usec, $sec) = explode(" ", microtime());      
   return ((float)$usec + (float)$sec);   
   }   
   $time_start = microtime_float();   
   $data=curl_multi_fetch($url_arr);   
   $time_end = microtime_float();   
   $time = $time_end - $time_start;   
   echo "耗时:{$time}";   
   ?>

   Copy after login

   耗时:0.316秒
   帅气吧整个页面访问后端接口的时间节省了一半
   
   

   3、curl相关参数
   curl_close — Close a cURL session
   curl_copy_handle — Copy a cURL handle along with all of its preferences
   curl_errno — Return the last error number
   curl_error — Return a string containing the last error for the current session
   curl_exec — Perform a cURL session
   curl_getinfo — Get information regarding a specific transfer
   curl_init — Initialize a cURL session
   curl_multi_add_handle — Add a normal cURL handle to a cURL multi handle
   curl_multi_close — Close a set of cURL handles
   curl_multi_exec — Run the sub-connections of the current cURL handle
   curl_multi_getcontent — Return the content of a cURL handle if CURLOPT_RETURNTRANSFER is set
   curl_multi_info_read — Get information about the current transfers
   curl_multi_init — Returns a new cURL multi handle
   curl_multi_remove_handle — Remove a multi handle from a set of cURL handles
   curl_multi_select — Wait for activity on any curl_multi connection
   curl_setopt_array — Set multiple options for a cURL transfer
   curl_setopt — Set an option for a cURL transfer
   curl_version — Gets cURL version information

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