PHP cURL curl_multi_exec() Function

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The PHP Client URL curl_multi_exec() function is used to execute multiple cURL sessions at the same time. This lets you make many HTTP requests at once, which can improve the performance of your application.

Syntax

Below is the syntax of the PHP cURL curl_multi_exec() function −

int curl_multi_exec ( resource $mh , int &$still_running )

Parameters

Following are the parameters required for the curl_multi_exec() function −

• $mh − It is the multi handle returned by curl_multi_init().

• $still_running − It is a pointer to an integer that will have the number of still running transfers.

Return Value

The curl_multi_exec() function returns one of the cURL codes listed in the Predefined Constants for cURL. Below are some of the codes listed −

• CURLM_CALL_MULTI_PERFORM − It shows that the function should be called again before the transfers are complete.

• CURLM_OK − It shows that the function has completed successfully.

• CURLM_BAD_HANDLE − The given handle is not a valid multi handle.

• CURLM_BAD_EASY_HANDLE − An easy handle was not valid.

• CURLM_OUT_OF_MEMORY − A memory allocation request failed.

• CURLM_INTERNAL_ERROR − An internal error occurred.

PHP Version

Introduced in core PHP 5, the curl_multi_exec() function works well with PHP 7, and PHP 8.

Example 1

Here is the basic example of how to use the PHP cURL curl_multi_exec() function to execute multiple handles simultaneously.

<?php
   // URLs to fetch & replace the URLs as per your need
   $urls = [
       "https://jsonplaceholder.typicode.com/todos/1",
       "https://jsonplaceholder.typicode.com/todos/2",
       "https://jsonplaceholder.typicode.com/todos/3",
   ];
   
   // Initialize multi handle
   $mh = curl_multi_init();
   
   // Array to store cURL handles
   $handles = [];
   
   // Create individual cURL handles for each URL
   foreach ($urls as $url) {
       $ch = curl_init();
       curl_setopt($ch, CURLOPT_URL, $url);
       curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
       curl_multi_add_handle($mh, $ch);
       $handles[] = $ch;
   }
   
   // Execute the multi handle
   $running = null;
   do {
       curl_multi_exec($mh, $running);
   } while ($running > 0);
   
   // Get and display responses
   foreach ($handles as $ch) {
       $response = curl_multi_getcontent($ch);
       echo $response . "<br>";
   }
   
   // Remove handles and close multi handle
   foreach ($handles as $ch) {
       curl_multi_remove_handle($mh, $ch);
       curl_close($ch);
   }
   curl_multi_close($mh);

Output

Here is the outcome of the following code −

{ "userId": 1, "id": 1, "title": "delectus aut autem", "completed": false }
{ "userId": 1, "id": 2, "title": "quis ut nam facilis et officia qui", "completed": false }
{ "userId": 1, "id": 3, "title": "fugiat veniam minus", "completed": false }

Example 2

In the below PHP code we will try to use the curl_multi_exec() function to handle different HTTP methods.

<?php
   // URLs and HTTP methods & replace the URLs as per your need
   $requests = [
      "GET" => "https://jsonplaceholder.typicode.com/posts/1",
      "POST" => "https://jsonplaceholder.typicode.com/todos",
      "PUT" => "https://jsonplaceholder.typicode.com/users/1",
   ];

   // Initialize multi handle
   $mh = curl_multi_init();

   // Array to store cURL handles
   $handles = [];

   // Create cURL handles for each request
   foreach ($requests as $method => $url) {
      $ch = curl_init();
      curl_setopt($ch, CURLOPT_URL, $url);
      curl_setopt($ch, CURLOPT_CUSTOMREQUEST, $method);
      curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
      curl_multi_add_handle($mh, $ch);
      $handles[] = $ch;
   }

   // Execute the multi handle
   $running = null;
   do {
      curl_multi_exec($mh, $running);
   } while ($running > 0);

   // Get and display responses
   foreach ($handles as $ch) {
      $response = curl_multi_getcontent($ch);
      echo $response . "<br>";
   }

   // Remove handles and close multi handle
   foreach ($handles as $ch) {
      curl_multi_remove_handle($mh, $ch);
      curl_close($ch);
   }
   curl_multi_close($mh);
?> 

Output

This will generate the below output −

{ "userId": 1, "id": 1, "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto" }
{ "id": 201 }
{ "id": 1 }

Example 3

Now we will use the curl_multi_exec() function to set different headers for each requests.

<?php
   // URLs and headers
   $requests = [
      "https://jsonplaceholder.typicode.com/todos/1" => [
         "User-Agent: MyCurlClient/1.0",
      ],
      "https://jsonplaceholder.typicode.com/users/1" => [
         "Authorization: Bearer my_token",
         "Content-Type: application/json",
      ],
   ];

   // Initialize multi handle
   $mh = curl_multi_init();

   // Array to store cURL handles
   $handles = [];

   // Create cURL handles with custom headers
   foreach ($requests as $url => $headers) {
      $ch = curl_init();
      curl_setopt($ch, CURLOPT_URL, $url);
      curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
      curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
      curl_multi_add_handle($mh, $ch);
      $handles[] = $ch;
   }

   // Execute the multi handle
   $running = null;
   do {
      curl_multi_exec($mh, $running);
   } while ($running > 0);

   // Get and display responses
   foreach ($handles as $ch) {
      $response = curl_multi_getcontent($ch);
      echo $response . "<br>";
   }

   // Remove handles and close multi handle
   foreach ($handles as $ch) {
      curl_multi_remove_handle($mh, $ch);
      curl_close($ch);
   }
   curl_multi_close($mh);
?> 

Output

This will create the below output −

{ "userId": 1, "id": 1, "title": "delectus aut autem", "completed": false }
{ "id": 1, "name": "Leanne Graham", "username": "Bret", "email": "[email protected]", "address": { "street": "Kulas Light", "suite": "Apt. 556", "city": "Gwenborough", "zipcode": "92998-3874", "geo": { "lat": "-37.3159", "lng": "81.1496" } }, "phone": "1-770-736-8031 x56442", "website": "hildegard.org", "company": { "name": "Romaguera-Crona", "catchPhrase": "Multi-layered client-server neural-net", "bs": "harness real-time e-markets" } }

Important Note

This function checks every handle in the stack. Whether a handle is required to read or write data is irrelevant when calling this method.