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Unable to load dynamic library php_curl.dll: Error message in PHP

PHP logoIn Windows, while trying to use "curl" extension with PHP 5.2/Apache 2; you may encounter a blank page. If you open up the error log file in Apache (%APACHE_HOME%\logs\error.log); you may see an error message as follows.

"PHP Warning: PHP Startup: Unable to load dynamic library '%PHP_HOME\\ext\\php_curl.dll' - The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log for more detail."

This error message can be caused due to some version conflicts on a set of DLLs that are already available inside %windows%\system32 directory.

First check the %windows%\system32 directory to see whether the following DLL files are already available.
curl logo
  1. libeay32.dll
  2. ssleay32.dll
If those are available, then you would be able to resolve the issue as follows. (However if they are not available, you would need to find some alternative solution).

Now you must first rename the above two DLL files. We did as follows by adding an .old extesion.
  1. libeay32.dll.old
  2. ssleay32.dll.old
Both these libeay32.dll and ssleay32.dll files are available inside your %PHP_HOME% directory. Now copy both of those DLL files into %windows%\system32 folder.

Now try to use the "curl" extension, and it will start to function properly. (Sometimes you may need to restart Windows).

However if this tip could not resolve your issue, make sure to restore the previous DLLs.


  1. This worked like a charm. (BTW the first time I ever read a solution on this issue).

  2. hi, I try your tutorial. but I still got these message :(

  3. I think you should copy the file php_curl.dll to %windows%\system32 directory

  4. [SOLVED]
    I couldn't make curl work on php-5.2.14. Installed php-5.2.13, and it works fine.


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