How to add filter for wordpress plugin?

Question

I have a really newbie question, but I'm really new to WordPress development. In the plugin that I'm using is using this filter.

if ( true === apply_filters( 'some_custom_filter', false ) ) {
   return $something;
}

Now I'd like to add_filter so it will return true how do I achieve that?

This is what I'm trying but doesn't work it always return false

public function setup_filters() {
    add_filter( 'some_custom_filter', array( $this, 'filter_suppress_the_content' ), 10, 3 );
}

public function filter_suppress_the_content() {
    return true;
}

This is the class.

private static $instance;
private static $wpcom_related_posts;

public static function get_instance() {
    if( ! isset( self::$instance ) ) {
        self::$instance = new Klazz;
        self::$instance->setup_filters();
    }

    return self::$instance;
}

public function setup_filters() {
    add_filter( 'some_custom_filter', array( $this, 'filter_suppress_the_content' ), 10, 1 );
}

public function filter_suppress_the_content( $false) {
    return true;
}

Answer 1

You are almost close.

add_filter( 'some_custom_filter', array( $this, 'filter_suppress_the_content' ), 10, 3 );
// the above line states that, the method `filter_suppress_the_content` should have three arguments, where you have used nothing.


public function filter_suppress_the_content() {
    return true;
}
// comparing your code, this method should have one argument

The solution:

public function setup_filters() {
  add_filter( 'some_custom_filter', array( $this, 'filter_suppress_the_content' ), 10, 1 );
}
public function filter_suppress_the_content( $false ){
    return true;
}