public static function _getCompatibleTransientKey($sSubject, $iAllowedCharacterLength = 45)
{
if (strlen($sSubject) <= $iAllowedCharacterLength) {
return $sSubject;
}
$_iPrefixLengthToKeep = $iAllowedCharacterLength - 33;
$_sPrefixToKeep = substr($sSubject, 0, $_iPrefixLengthToKeep - 1);
return $_sPrefixToKeep . '_' . md5($sSubject);
}