How to use mce_css filter in WordPress

To dive in, you’ll first need to register this filter with add_filter. You can drop this code into your theme’s functions.php file or, if you’re like me and prefer things neat, throw it into a custom WordPress Plugin. This way, when you update your theme, nothing goes haywire.

Oh, and sometimes you might want to ditch a registered hook—no worries, remove_filter has got your back. Let’s see some live examples to get a better hang of it.

Example 1: Basic Usage

Here’s a simple way to use the mce_css filter:

add_filter( 'mce_css', 'weplugins_plugin_mce_css' );
    function weplugins_plugin_mce_css( $mce_css ) {
        if ( ! empty( $mce_css ) )
            $mce_css .= ',';
        $mce_css .= plugins_url( 'editor.css', __FILE__ );
        return $mce_css;
    }

Example 2: Modifying Stylesheets

Want to tweak the stylesheets? Check this out:

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

Example 3: Removing a Filter

Need to remove a hook callback? Here’s how:

remove_filter( "mce_css", "weplugins_modify_mce_css_defaults", 10, 1 );

Key Points: Always ensure that you use the correct callback function name, priority, and number of arguments when removing a hook callback.