get_list_hooked.php

<?php
function wptq_hooked_action_for( $hook_name = '' ){
    global $wp_filter;
    if( empty( $hook_name ) || !isset( $wp_filter[$hook_name] ) || !is_object( $wp_filter[$hook_name] ) ){
        return;
    }
    $list_hooked = array();
    
    $callbacks = $wp_filter[$hook_name]->callbacks;
    if( !empty( $callbacks ) ){
        foreach( $callbacks as $key=>$value ){
            if( is_array( $value ) && !empty( $value ) ){
                foreach( $value as $k=>$v ){
                    if( array_key_exists( 'function', $v ) && !is_array( $v['function'] ) ){
                        $list_hooked[] = array(
                            'type'          => 'function',
                            'function_name' => $v['function'],
                            'accepted_args' => $v['accepted_args'],
                            'priority'      => $key
                        );
                    }elseif( array_key_exists( 'function', $v ) && is_array( $v['function'] ) && is_object( $v['function'][0] ) && !empty( $v['function'][1] ) ){
                        $list_hooked[] = array(
                            'type'          => 'method',
                            'object_name'   => get_class( $v['function'][0]),
                            'method_name'   => $v['function'][1],
                            'accepted_args' => $v['accepted_args'],
                            'priority'      => $key
                        );
                    }
                }
            }
        }
    }
    echo "<pre>";
    print_r( $list_hooked );
    echo "</pre>";
}

//Example
wptq_hooked_action_for( 'wp_head' );