<?php
/**
* Shared validation logic for 'rel' attribute on <a>, <area>, <form> and <link> elements,
* as defined by the HTML5 spec and the MicroFormats link type extensions tables.
*
* @see https://html.spec.whatwg.org/multipage/links.html#linkTypes
*/
abstract class HTMLPurifier_AttrDef_HTML5_Rel extends HTMLPurifier_AttrDef
{
/**
* Lookup table for valid rel values.
* Stored as a static variable to minimize serialization footprint.
* @var array
*/
protected static $values = array();
/**
* Lazy loaded lookup for allowed rel values, based on provided config.
* @var array
*/
protected $allowed;
/**
* @param string $string
* @param HTMLPurifier_Config $config
* @param HTMLPurifier_Context $context
* @return bool|string
*/
public function validate($string, $config, $context)
{
if ($this->allowed === null) {
$allowedRel = (array) $config->get('Attr.AllowedRel');
if (empty($allowedRel)) {
$allowed = array();
} else {
$allowed = array_intersect_key($allowedRel, static::$values);
}
$this->allowed = $allowed;
}
$string = $this->parseCDATA($string);
$parts = explode(' ', $string);
$result = array();
foreach ($parts as $part) {
// Link type keywords are always ASCII case-insensitive, and must be compared as such.
// https://html.spec.whatwg.org/multipage/links.html#linkTypes
$part = strtolower(trim($part));
if (!isset($this->allowed[$part])) {
continue;
}
$result[$part] = true;
}
if (empty($result)) {
return false;
}
return implode(' ', array_keys($result));
}
}