Problem with function in hook element

Hi there, I'm adding this snippet to a hook element, but this partly breaks the site

<?php  
hmk_show_matching_percentage();  
?>

This is the function, which is working, but I want to control the position of it with a hook. It does not matter which hook I select, same result.

/**
  * Load the matching stuff only if BuddyPress is active.
  */
  function mp_bp_match_init() {

      require_once('src/class.settings-api.php');
  		require_once('mp-settings.php');

      new WeDevs_Settings_API_Match();

      add_action('wp_footer', array($this, 'hmk_script'), 100);

 

<blockquote>Function from this line:</blockquote>

  add_action('bp_profile_header_meta', array($this, 'hmk_show_matching_percentage'), 10);
      add_action('bp_directory_members_item', array($this, 'hmk_matching_percentage_button'), 10);

      add_shortcode( 'mp_match_percentage', array($this, 'mp_match_percentage_function'));

      add_action('wp_ajax_hmk_get_percentage', array($this, 'hmk_get_percentage_function'), 100);
      add_action('wp_ajax_nopriv_hmk_get_percentage', array($this, 'hmk_get_percentage_function'), 100);

   }

Any idea why this code snippet

<?php  
hmk_show_matching_percentage();  
?>

pasted in a hook element is breaking the site?

Thanks!