The PHP extension provided in uuid-php package seems broken. Various methods require argument passed by reference, which is not supported in PHP 5.4. $ php -r 'echo uuid_create();' Warning: uuid_create() expects exactly 1 parameter, 0 given ... 1 $ php -r 'echo uuid_create($ctx);' Warning: uuid_create(): uuid_create: parameter wasn't passed by reference ... 1 $ php -r 'echo uuid_create(&$ctx);' Fatal error: Call-time pass-by-reference has been removed ... It seems this extension is not required by any package. More, Horde detects this extension and try to use it, when installed, but fails as it expects the uuid extension from pecl. So, horde package need to conflicts with this extension. I have php-pecl-uuid package near to be ready, but this is not a drop in replacement (API are quite different).