How to pass a variable $ _ GET in a page?
Try the following code:

    $items['candidate/%user'] = array(
      'title'            =&gt; t('My candidate space'),
      'page callback'    =&gt; 'cel_configuration_custom_page',
      'page arguments'   =&gt; array(1),
      'access arguments' =&gt; array('access user profiles'),
    );

    function cel_configuration_custom_page($account){
      return 'Custom page for ' . $account-&gt;name;
    }


You can't use %candidate as an argument for user accounts. Also, if you want to restrict access by a particular permission, don't set access callback to TRUE as that will grant access to everyone.