How to use query_vars filter in WordPress

query_vars filter

Allows (publicly allowed) query vars to be added, removed, or changed prior to executing the query. Needed to allow custom rewrite rules using your own arguments to work, or any other custom query variables you want to be publicly available.

To use the query_vars filter, first you have to register it using add_filter. You can write this code into functions.php of your activated theme or in a custom WordPress Plugin.

We at WePlugins, always prefer to create a custom WordPress Plugin while using hooks so nothing breaks when you update your WordPress Theme in the future.

In the below live example, we have defined a function modify_query_vars_defaults which takes 1 parameter and we registered it using add_filter. The first parameter query_vars is the name of the hook, the second parameter modify_query_vars_defaults is the name of the function which needs to be called, the third parameter is the priority of calling the hook if the same hook is used multiple times and the last parameter is the number of arguments (if any) to be passed in the registered function.

Sometimes, you have to remove a registered hook so you can use remove_filter to remove the query_vars filter.

Parameters

Below the 1 parameter is required to use this hook.

• $public_query_vars: (string[]) The array of allowed query variable names.

Live Example 1: Adding a Custom Query Var

In this example, we add a custom query variable called custom_query_var.

    function weplugins_query_vars( $qvars ) {
        $qvars[] = 'custom_query_var';
        return $qvars;
    }
    add_filter( 'query_vars', 'weplugins_query_vars' );
    

Live Example 2: Modifying Default Query Vars

This example shows how you can modify the default query vars.

    function weplugins_modify_query_vars_defaults($public_query_vars) {
        // Update the $public_query_vars variable according to your website requirements and return this variable. You can modify the $public_query_vars variable conditionally too if you want.
        return $public_query_vars;
    }
    // add the filter
    add_filter( "query_vars", "weplugins_modify_query_vars_defaults", 10, 1 );
    

Live Example 3: Removing a Hook Callback

To remove a hook callback, use the example below.

    remove_filter( "query_vars", "weplugins_modify_query_vars_defaults", 10, 1 );
    

Please make sure to provide the same callback function name, priority and number of arguments while removing the hook callback.

Contact Us

If you need any customization or help, feel free to contact us.