modules/user/views_plugin_argument_validate_user.inc

<?php

class views_plugin_argument_validate_user extends views_plugin_argument_validate {
  function option_definition() {
    $options = parent::option_definition();
    $options['type'] = array('default' => 'uid');
    $options['restrict_roles'] = array('default' => FALSE);
    $options['roles'] = array('default' => array());

    return $options;
  }

  function options_form(&$form, &$form_state) {
    $form['type'] = array(
      '#type' => 'radios',
      '#title' => t('Type of user filter value to allow'),
      '#options' => array(
        'uid' => t('Only allow numeric UIDs'),
        'name' => t('Only allow string usernames'),
        'either' => t('Allow both numeric UIDs and string usernames'),
      ),
      '#default_value' => $this->options['type'],
    );

    $form['restrict_roles'] = array(
      '#type' => 'checkbox',
      '#title' => t('Restrict user based on role'),
      '#default_value' => $this->options['restrict_roles'],
    );

    $form['roles'] = array(
      '#type' => 'checkboxes',
      '#prefix' => '<div id="edit-options-validate-options-user-roles-wrapper">',
      '#suffix' => '</div>',
      '#title' => t('Restrict to the selected roles'),
      '#options' => array_map('check_plain', user_roles(TRUE)),
      '#default_value' => $this->options['roles'],
      '#description' => t('If no roles are selected, users from any role will be allowed.'),
      '#dependency' => array(
        'edit-options-validate-options-user-restrict-roles' => array(1),
      ),
    );
  }

  function options_submit(&$form, &$form_state, &$options = array()) {
    // filter trash out of the options so we don't store giant unnecessary arrays
    $options['roles'] = array_filter($options['roles']);
  }

  function convert_options(&$options) {
    if (!isset($options['type']) && isset($this->argument->options['validate_user_argument_type'])) {
      $options['type'] = $this->argument->options['validate_user_argument_type'];
      $options['restrict_roles'] = $this->argument->options['validate_user_restrict_roles'];
      $options['roles'] = $this->argument->options['validate_user_roles'];
    }
  }

  function validate_argument($argument) {
    $type = $this->options['type'];
    // is_numeric() can return false positives, so we ensure it's an integer.
    // However, is_integer() will always fail, since $argument is a string.
    if (is_numeric($argument) && $argument == (int)$argument) {
      if ($type == 'uid' || $type == 'either') {
        if ($argument == $GLOBALS['user']->uid) {
          // If you assign an object to a variable in PHP, the variable
          // automatically acts as a reference, not a copy, so we use
          // clone to ensure that we don't actually mess with the
          // real global $user object.
          $account = clone $GLOBALS['user'];
        }
        $where = 'uid = :argument';
      }
    }
    else {
      if ($type == 'name' || $type == 'either') {
        $name = !empty($GLOBALS['user']->name) ? $GLOBALS['user']->name : variable_get('anonymous', t('Anonymous'));
        if ($argument == $name) {
          $account = clone $GLOBALS['user'];
        }
        $where = "name = :argument";
      }
    }

    // If we don't have a WHERE clause, the argument is invalid.
    if (empty($where)) {
      return FALSE;
    }

    if (!isset($account)) {
      $query = "SELECT uid, name FROM {users} WHERE $where";
      $account = db_query($query, array(':argument' => $argument))->fetchObject();
    }
    if (empty($account)) {
      // User not found.
      return FALSE;
    }

    // See if we're filtering users based on roles.
    if (!empty($this->options['restrict_roles']) && !empty($this->options['roles'])) {
      $roles = $this->options['roles'];
      $account->roles = array();
      $account->roles[] = $account->uid ? DRUPAL_AUTHENTICATED_RID : DRUPAL_ANONYMOUS_RID;
      $result = db_query('SELECT rid FROM {users_roles} WHERE uid = :uid', array(':uid' => $account->uid));
      foreach ($result as $role) {
        $account->roles[] = $role->rid;
      }
      if (!(bool) array_intersect($account->roles, $roles)) {
        return FALSE;
      }
    }

    $this->argument->argument = $account->uid;
    $this->argument->validated_title = isset($account->name) ? check_plain($account->name) : check_plain(variable_get('anonymous', t('Anonymous')));
    return TRUE;
  }

  function process_summary_arguments(&$args) {
    // If the validation says the input is an username, we should reverse the
    // argument so it works for example for generation summary urls.
    $uids_arg_keys = array_flip($args);
    if ($this->options['type'] == 'name') {
      $users = user_load_multiple($args);
      foreach ($users as $uid => $account) {
        $args[$uids_arg_keys[$uid]] = $account->name;
      }
    }
  }
}