How to use pre_kses filter in WordPress

pre_kses filter

Filters content to be run through KSES.

To use the pre_kses filter, first, you have to register it using add_filter. You can write this code into the 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 weplugins_modify_pre_kses_defaults which takes 3 parameters and we registered using add_filter. The first parameter pre_kses is the name of the hook, the second parameter weplugins_modify_pre_kses_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 pre_kses filter.

Parameters

Below are the 3 parameters required to use this hook.

• $string : (string) Content to filter through KSES.
• $allowed_html : (array[]|string) An array of allowed HTML elements and attributes, or a context name such as ‘post’. See wp_kses_allowed_html() for the list of accepted context names.
• $allowed_protocols : (string[]) Array of allowed URL protocols.

Live Example

Example 1: Basic Usage

Below is an example of how you can use this hook.

    function weplugins_modify_pre_kses_defaults($string, $allowed_html, $allowed_protocols) { 
        // Update the $string variable according to your website requirements and return this variable. You can modify the $string variable conditionally too if you want.
        return $string; 
    }
    // add the filter
    add_filter("pre_kses", "weplugins_modify_pre_kses_defaults", 10, 3);
    

Example 2: Conditional Modification

In this example, we will conditionally modify the string based on certain criteria.

    function weplugins_modify_pre_kses_conditionally($string, $allowed_html, $allowed_protocols) {
        if (str_contains($string, 'special-keyword')) {
            $string = str_replace('special-keyword', 'replacement', $string);
        }
        return $string;
    }
    // add the filter
    add_filter("pre_kses", "weplugins_modify_pre_kses_conditionally", 10, 3);
    

Example 3: Removing a Hook Callback

To remove a hook callback, use the example below. Make sure to provide the same callback function name, priority, and number of arguments while removing the hook callback.

    remove_filter("pre_kses", "weplugins_modify_pre_kses_defaults", 10, 3);