Title: ERROR: Call to undefined function hash_equals
Last modified: September 1, 2016

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# ERROR: Call to undefined function hash_equals

 *  Resolved [Donghyeok Kang](https://wordpress.org/support/users/wolfkang/)
 * (@wolfkang)
 * [9 years, 11 months ago](https://wordpress.org/support/topic/error-call-to-undefined-function-hash_equals/)
 * Hi,
    I’m using PHP 5.5. I got this error.
 * > Call to undefined function hash_equals
 * Please check this out.
    Thanks.
 * [https://wordpress.org/plugins/wordfence/](https://wordpress.org/plugins/wordfence/)

Viewing 4 replies - 1 through 4 (of 4 total)

 *  [wfalaa](https://wordpress.org/support/users/wfalaa/)
 * (@wfalaa)
 * [9 years, 11 months ago](https://wordpress.org/support/topic/error-call-to-undefined-function-hash_equals/#post-7533518)
 * Hi,
    According to [PHP documentation](http://php.net/manual/en/function.hash-equals.php),
   this function is defined within (PHP 5 >= 5.6.0, PHP 7), so any PHP version older
   than 5.6 will not have this function by default.
 * It’s recommended to upgrade PHP version to at least 5.6 as mentioned in the [WordPress requirements guide](https://wordpress.org/about/requirements/),
   you can ask your hosting provider about that, most hosting providers now support
   changing PHP version from your server control panel.
 * Thanks.
 *  Thread Starter [Donghyeok Kang](https://wordpress.org/support/users/wolfkang/)
 * (@wolfkang)
 * [9 years, 11 months ago](https://wordpress.org/support/topic/error-call-to-undefined-function-hash_equals/#post-7533532)
 * Hey,
    I’m sorry to hear that. Does every Wodrdfence users use PHP 5.6 or 7.0?
   What you said is just a recommendation. I suggest that you shoud write “Wordfence
   requires PHP 5.6 or later” in the plugin description or append the hash_equals
   function in the case of the older PHP version. Thanks.
 *  [wfalaa](https://wordpress.org/support/users/wfalaa/)
 * (@wfalaa)
 * [9 years, 11 months ago](https://wordpress.org/support/topic/error-call-to-undefined-function-hash_equals/#post-7533565)
 * I can see WordPress [includes this function since version 3.9.2](https://developer.wordpress.org/reference/functions/hash_equals/),
   could you please confirm you are running the latest WordPress version?
 * Also, try deactivating all your plugins (except Wordfence) and re-check this 
   issue, and please post the whole error message you get in the error log file,
   it will help us to investigate this issue in details.
 * Keep me updated,
    Thanks.
 *  Thread Starter [Donghyeok Kang](https://wordpress.org/support/users/wolfkang/)
 * (@wolfkang)
 * [9 years, 11 months ago](https://wordpress.org/support/topic/error-call-to-undefined-function-hash_equals/#post-7533578)
 * I solved this.
    The WordPress version of my site was 3.8. I upgraded and solved
   it. Thank you so much.

Viewing 4 replies - 1 through 4 (of 4 total)

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 * 4 replies
 * 2 participants
 * Last reply from: [Donghyeok Kang](https://wordpress.org/support/users/wolfkang/)
 * Last activity: [9 years, 11 months ago](https://wordpress.org/support/topic/error-call-to-undefined-function-hash_equals/#post-7533578)
 * Status: resolved