azure-storage-common/src/Common/Internal/Utilities.php
public static function getGuid()
    {
        // @codingStandardsIgnoreStart

        return sprintf(
            '%04x%04x-%04x-%04x-%02x%02x-%04x%04x%04x',
            mt_rand(0, 65535),
            mt_rand(0, 65535),          // 32 bits for "time_low"
            mt_rand(0, 65535),          // 16 bits for "time_mid"
            mt_rand(0, 4096) + 16384,   // 16 bits for "time_hi_and_version", with
                                        // the most significant 4 bits being 0100
                                        // to indicate randomly generated version
            mt_rand(0, 64) + 128,       // 8 bits  for "clock_seq_hi", with
                                        // the most significant 2 bits being 10,
                                        // required by version 4 GUIDs.
            mt_rand(0, 256),            // 8 bits  for "clock_seq_low"
            mt_rand(0, 65535),          // 16 bits for "node 0" and "node 1"
            mt_rand(0, 65535),          // 16 bits for "node 2" and "node 3"
            mt_rand(0, 65535)           // 16 bits for "node 4" and "node 5"
        );

        // @codingStandardsIgnoreEnd
    }
public static function getGuid()
    {
        // @codingStandardsIgnoreStart

        return sprintf(
            '%04x%04x-%04x-%04x-%02x%02x-%04x%04x%04x',
            mt_rand(0, 65535),
            mt_rand(0, 65535),          // 32 bits for "time_low"
            mt_rand(0, 65535),          // 16 bits for "time_mid"
            mt_rand(0, 4096) + 16384,   // 16 bits for "time_hi_and_version", with
                                        // the most significant 4 bits being 0100
                                        // to indicate randomly generated version
            mt_rand(0, 64) + 128,       // 8 bits  for "clock_seq_hi", with
                                        // the most significant 2 bits being 10,
                                        // required by version 4 GUIDs.
            mt_rand(0, 256),            // 8 bits  for "clock_seq_low"
            mt_rand(0, 65535),          // 16 bits for "node 0" and "node 1"
            mt_rand(0, 65535),          // 16 bits for "node 2" and "node 3"
            mt_rand(0, 65535)           // 16 bits for "node 4" and "node 5"
        );

        // @codingStandardsIgnoreEnd
    }
Returns a string representation of a version 4 GUID, which uses random
numbers.There are 6 reserved bits, and the GUIDs have this format:
xxxxxxxx-xxxx-4xxx-[8|9|a|b]xxx-xxxxxxxxxxxx
where 'x' is a hexadecimal digit, 0-9a-f.

See http://tools.ietf.org/html/rfc4122 for more information.

Note: This function is available on all platforms, while the
com_create_guid() is only available for Windows.

@return string A new GUID.