protected static function hex2bin($hexstr)
{
if (\function_exists('hex2bin')) {
return \hex2bin($hexstr);
}
$n = \strlen($hexstr);
$sbin = '';
$i = 0;
while ($i < $n) {
$a = \substr($hexstr, $i, 2);
$c = \pack('H*', $a);
$sbin .= $c;
$i += 2;
}
return $sbin;
}