Drupal template helpers to render values.

template.php

<?php
/** 
 * Renders a value cleaned. Simply pulls value through check_plain.
 *
 * Example usage:
 * @code
 *  r('foo'); //=> "Foo"
 *  r('<script alert(infected)>Foo'); //=> "Foo"
 *  r("<em>123</em>"); //=> 123
 * @endcode
 * 
 * @param $value Mixed
 *   The value to be printed. Value must be of a printable type. 
 * @return
 *   Nothing. Function prints value directly.
 */
function r($value) {
  print check_plain($value);
}

/** 
 * Renders a value raw.
 *
 * Example usage:
 * @code
 *  r_raw('foo'); //=> "Foo"
 *  r_raw('<script alert(infected)>Foo'); //=> "<script alert(infected)>Foo"
 *  r_raw("<em>123</em>"); //=> "<em>123</em>"
 * @endcode
 * 
 * @param $value Mixed
 *   The value to be printed. Value must be of a printable type. 
 * @return
 *   Nothing. Function prints value directly.
 */
function r_raw($value) {
  print $value;
}

/** 
 * Renders a field, joined
 *
 * Example usage:
 * @code
 *  r_join(', ', $field_hometown); //=> "Nijmegen, <em>GLD</em>"
 *  r_join(', ', $field_hometown, 'safe'); //=> "Nijmegen, GLD"
 *  r_join(', ', $field_hometown, 'value'); //=> "Nijmegen<script alert(SECURITY BREACH)>, <em>GLD</em>"
 * @endcode
 * 
 * @param $glue String
 *   Used to join the values. Will be passed along to implode().
 * @param $field Array
 *   A field, as presented to the (node) templates. Consists of a list of values
 *   separated into value_types. E.g.
 *  ["field_hometown"]=>
 *    array(1) {
 *       [0]=>
 *       array(3) {
 *         ["value"]=>
 *         string(10) "Heerenveen"
 *         ["safe"]=>
 *         string(10) "Heerenveen"
 *         ["view"]=>
 *         string(10) "Heerenveen"
 *       }
 *     }
 * @param $value_type String, optional defaults to 'view'
 *   The value_type to be used. Normally one of "view", "safe" or "value".
 *   See example usage for how these /might/ be filed. In general they won't differ
 *   too much. Never use "value" unless you are very sure about the safety of the value. 
 * @return
 *   Nothing. Function prints value directly.
 */
function r_join($glue, $field, $value_type = 'view') {
  foreach($field as $field_value) {
    $values[] = $field_value[$value_type];
  }
  print join($glue, $values);
}
?>

As discussed on http://identi.ca/conversation/57034397#notice-57540830: r_join could, or should have $glue otional and therefore second argument. But that would be inconsistent with join() and implode(). Which, being "PHPish" are wrong too, but at least consistently wrong.