/**
  * Returns the ID of the class attribute with the given ID or false if no class/attribute by that identifier
  * is found. If multiple classes have the same identifier, the first found is returned.
  *
  * @param string $identifier
  * @return int|bool
  */
 static function classAttributeIDByIdentifier($identifier)
 {
     return eZContentClassAttribute::classAttributeIDByIdentifier($identifier);
 }
 public static function keyword($params)
 {
     $sqlTables = '';
     $sqlJoins = '';
     $keyword = isset($params['keyword']) ? $params['keyword'] : false;
     $attribute = isset($params['attribute']) ? $params['attribute'] : false;
     if ($keyword === false && is_string($keyword) && $keyword != '') {
         return array();
     }
     $db = eZDB::instance();
     $sqlKeyword = $db->escapeString($keyword);
     $sqlJoins .= 'coa_related_by_keyword' . $params['index'] . '.contentobject_id = ezcontentobject.id AND ' . 'coa_related_by_keyword' . $params['index'] . '.version = ezcontentobject.current_version AND ';
     $sqlJoins .= eZContentLanguage::sqlFilter('coa_related_by_keyword' . $params['index'], 'ezcontentobject') . ' AND ';
     if ($attribute !== false) {
         $attributeID = eZContentClassAttribute::classAttributeIDByIdentifier($attribute);
         if ($attributeID) {
             $sqlJoins .= 'coa_related_by_keyword' . $params['index'] . '.contentclassattribute_id = ' . $attributeID . ' AND ';
         }
     }
     $sqlJoins .= 'coa_related_by_keyword' . $params['index'] . '.id = kal_related_by_keyword' . $params['index'] . '.objectattribute_id AND ' . 'kal_related_by_keyword' . $params['index'] . '.keyword_id = k_related_by_keyword' . $params['index'] . '.id AND ';
     $sqlJoins .= 'k_related_by_keyword' . $params['index'] . ".keyword = '" . $sqlKeyword . "' AND";
     $sqlTables .= ', ezcontentobject_attribute coa_related_by_keyword' . $params['index'] . ', ' . 'ezkeyword_attribute_link kal_related_by_keyword' . $params['index'] . ', ' . 'ezkeyword k_related_by_keyword' . $params['index'];
     return array('tables' => $sqlTables, 'joins' => $sqlJoins);
 }