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How to Use the curl_share_init Function in PHP? A Quick Guide to This Shared Handle Feature

gitbox 2025-07-12

When making network requests in PHP, cURL is a commonly used library that allows us to communicate via HTTP with other servers. However, in some situations, we may need to share certain resources (like cookies, file descriptors, etc.) across multiple cURL handles. This is where the curl_share_init function comes into play.

What is curl_share_init?

curl_share_init() is a PHP cURL function used to initialize a shared handle. This shared handle can be used across multiple cURL sessions, enabling them to share specific resources such as session cookies, DNS cache, file descriptors, and more.

Using curl_share_init() helps avoid loading the same resources repeatedly between multiple requests, improving performance and reducing system overhead. The function returns a shared handle, which you can then configure using other functions (like curl_setopt) to set parameters related to the shared handle, and finally release with curl_share_close.

Basic Syntax

<span><span><span class="hljs-variable">$share</span></span><span> = </span><span><span class="hljs-title function_ invoke__">curl_share_init</span></span><span>();
</span></span>

When you call this function, it returns a shared handle $share, which will be used to share resources among multiple cURL sessions. You can use this handle to control the behavior of shared resources.

curl_share_setopt Function

Once the shared handle is successfully initialized, you can use curl_share_setopt to specify which resources can be shared between sessions. Common shared resources include:

  • CURLOPT_SHARE: Used to specify which resources will be shared. You can use CURLSHOPT_SHARE to enable resource sharing, or CURLSHOPT_UNSHARE to stop sharing.

Types of Shared Resources

  • CURLSHOPT_SHARE (Shared Cookies): Multiple sessions share the same cookie data.

  • CURLSHOPT_SHARE (Shared DNS Cache): Multiple sessions share the same DNS resolution cache.

  • CURLSHOPT_SHARE (Shared File Descriptors): Shares file descriptors, useful when multiple cURL sessions need to read the same file.

Example Code

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// Initialize shared handle</span></span>
</span><span><span class="hljs-variable">$share</span></span><span> = </span><span><span class="hljs-title function_ invoke__">curl_share_init</span></span><span>();
<p></span>// Set shared resource (e.g., share cookies)<br>
</span>curl_share_setopt($share, CURLSHOPT_SHARE, CURL_LOCK_DATA_COOKIE);</p>
<p></span>// Initialize cURL handle 1<br>
</span>$ch1 = </span>curl_init();<br>
</span>curl_setopt($ch1, CURLOPT_URL, </span>'<a rel="noopener" target="_new" class="cursor-pointer">http://example.com'</span></span</a>>);<br>
curl_setopt($ch1, CURLOPT_SHARE, $share);</p>
<p></span>// Initialize cURL handle 2<br>
</span>$ch2 = </span>curl_init();<br>
</span>curl_setopt($ch2, CURLOPT_URL, </span>'<a rel="noopener" target="_new" class="cursor-pointer">http://example.org'</span></span</a>>);<br>
curl_setopt($ch2, CURLOPT_SHARE, $share);</p>
<p></span>// Execute cURL requests<br>
</span>curl_exec($ch1);<br>
</span>curl_exec($ch2);</p>
<p></span>// Close cURL handles<br>
</span>curl_close($ch1);<br>
</span>curl_close($ch2);</p>
<p></span>// Close shared handle<br>
</span>curl_share_close($share);<br>
</span>?><br>
</span></span>

In the example above, we initialize a shared handle $share and configure it to share cookie data. Then, two cURL handles $ch1 and $ch2 are created, both set to use the same shared handle. Finally, the requests are executed, and all cURL handles along with the shared handle are closed.

Use Cases

curl_share_init is very useful for sharing resources across multiple cURL requests, especially in the following scenarios:

  1. Sharing cookies across multiple requests: When performing multiple HTTP requests that require maintaining the same session (such as logged-in session states), sharing cookies is beneficial.

  2. Sharing DNS cache: When making multiple network requests to servers under the same domain, sharing DNS resolution cache can reduce DNS lookup overhead.

  3. Sharing file descriptors: When multiple requests need to read the same file resource, sharing file descriptors helps optimize file reading efficiency.

Important Notes

  1. Concurrent execution: When multiple cURL sessions share the same shared handle, ensure you manage concurrency properly to avoid race conditions. For example, cURL sessions might access shared resources simultaneously, so thread safety must be guaranteed.

  2. Resource sharing limitations: Although curl_share_init provides resource sharing capabilities, not all resources can be shared. Understanding which resource types cURL supports for sharing is important.

  3. Lifecycle of the shared handle: Since the shared handle shares resources across multiple cURL sessions, it should only be closed after all cURL sessions have completed, to ensure proper resource cleanup.

Conclusion

curl_share_init offers an efficient resource sharing mechanism for PHP’s cURL, especially useful when you need to share resources between multiple HTTP requests. By using shared handles wisely, you can reduce redundant work and improve your program’s performance. Mastering curl_share_init is valuable for enhancing the flexibility and efficiency of your cURL operations.

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