Determine if the given identifier is an XRI ID.
function _openid_is_xri($identifier) {
// Strip the xri:// scheme from the identifier if present.
if (stripos($identifier, 'xri://') === 0) {
$identifier = substr($identifier, 6);
}
// Test whether the identifier starts with an XRI global context symbol or (.
$firstchar = substr($identifier, 0, 1);
if (strpos("=@+\$!(", $firstchar) !== FALSE) {
return TRUE;
}
return FALSE;
}