public static function GenerateUID($short = false, $startWithLetter = false)
{
$pr_bits = false;
if (!$pr_bits) {
if (DIRECTORY_SEPARATOR !== '\\' && ($fp = @fopen('/dev/urandom', 'rb')) !== false) {
$pr_bits .= fread($fp, 16);
fclose($fp);
} else {
// If /dev/urandom isn't available (eg: in non-unix systems), use mt_rand().
$pr_bits = "";
for ($cnt = 0; $cnt < 16; $cnt++) {
$pr_bits .= chr(mt_rand(0, 255));
}
}
}
$time_low = bin2hex(substr($pr_bits, 0, 4));
$time_mid = bin2hex(substr($pr_bits, 4, 2));
$time_hi_and_version = bin2hex(substr($pr_bits, 6, 2));
$clock_seq_hi_and_reserved = bin2hex(substr($pr_bits, 8, 2));
$node = bin2hex(substr($pr_bits, 10, 6));
/**
* Set the four most significant bits (bits 12 through 15) of the
* time_hi_and_version field to the 4-bit version number from
* Section 4.1.3.
* @see http://tools.ietf.org/html/rfc4122#section-4.1.3
*/
$time_hi_and_version = hexdec($time_hi_and_version);
$time_hi_and_version = $time_hi_and_version >> 4;
$time_hi_and_version = $time_hi_and_version | 0x4000;
/**
* Set the two most significant bits (bits 6 and 7) of the
* clock_seq_hi_and_reserved to zero and one, respectively.
*/
$clock_seq_hi_and_reserved = hexdec($clock_seq_hi_and_reserved);
$clock_seq_hi_and_reserved = $clock_seq_hi_and_reserved >> 2;
$clock_seq_hi_and_reserved = $clock_seq_hi_and_reserved | 0x8000;
if ($short) {
return sprintf('%012s', $node);
}
if ($startWithLetter) {
if (!preg_match("/^[a-z]+[a-z0-9]*\$/", $time_low)) {
$rand_char = chr(rand(97, 102));
$time_low = $rand_char . substr($time_low, 1);
}
}
return sprintf('%08s-%04s-%04x-%04x-%012s', $time_low, $time_mid, $time_hi_and_version, $clock_seq_hi_and_reserved, $node);
}