Title: PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback,
Last modified: June 7, 2019

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# PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback,

 *  [ilardo75](https://wordpress.org/support/users/ilardo75/)
 * (@ilardo75)
 * [7 years ago](https://wordpress.org/support/topic/php-warning-call_user_func_array-expects-parameter-1-to-be-a-valid-callback-4/)
 * Hi,
 * We are receiving this error when using Pos.
 * [error] 105685#105685: *98838 FastCGI sent in stderr: “PHP message: PHP Warning:
   call_user_func_array() expects parameter 1 to be a valid callback, no array or
   string given in /public/wp-includes/class-wp-hook.php on line 286” while reading
   response header from upstream, client: request: “POST /wp-json/wc/v3/orders HTTP/
   1.0”, upstream: “fastcgi://unix:/var/run/php7.3.sock:”, host: “www.”, referrer:“/
   pos/”
 * We have disabled all other plugins except woocommerce and pos.
 * We are using php 7.2 and have tested with php 7.3 and the same problem appears.
 * We are using wordpress 5.2.1
 * So we would be very convinced that the error comes from pos. Everything works
   fine. But the error is present. So not anything fatal.
 * Thanks

The topic ‘PHP Warning: call_user_func_array() expects parameter 1 to be a valid
callback,’ is closed to new replies.

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 * 0 replies
 * 1 participant
 * Last reply from: [ilardo75](https://wordpress.org/support/users/ilardo75/)
 * Last activity: [7 years ago](https://wordpress.org/support/topic/php-warning-call_user_func_array-expects-parameter-1-to-be-a-valid-callback-4/)
 * Status: not resolved