I created a plugin to override a theme's function. As I learn that function in plugin loads first but I got an error

Fatal error: Cannot redeclare wooc_extra_register_fields() (previously declared in ****/themes/****/functions.php:247) in ***/plugins/custom-plugin/custom-plugin.php on line 89

Not sure what I am doing wrong. Also put theme's functions need to be override in if !function exist. So what is the right way to override a theme function wrap in !function exist using a plugin??


2 Answers 2

In wp-settings.php, WordPress first checks for any must-use plugins (plugins in the optional mu-plugins folder) and loads those.

Then, if you're running a multisite installation, it checks for plugins that are network-activated and loads those.


For your situation it would be best to wrap the plugin in function_exists

if ( ! function_exists( 'wooc_extra_register_fields' ) ) {
    function wooc_extra_register_fields() {

in the parent theme, as this makes the functions of the theme pluggable. You can then create a child theme and redeclare the function in the child theme's functions.php

  • I already do wrap theme function on !function_exists. but the functions in theme are loaded before plugin so it doesn't help Dec 16, 2016 at 10:22
  • Tunji is correct. If you put the code in the child theme, it's functions.php will be loaded before the parent's functions.php
    – johnh10
    Dec 16, 2016 at 14:11

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