Can be useful, for instance, if you generate identifiers simultaneously on several hosts that might happen to generate the identifier at the same microsecond.
With an empty prefix, the returned string will
be 13 characters long. If more_entropy is
TRUE, it will be 23 characters.
If set to
TRUE, uniqid() will add additional
entropy (using the combined linear congruential generator) at the end
of the return value, which should make the results more unique.
If you need a unique identifier or token and you intend to give out that token to the user via the network (i.e. session cookies), it is recommended that you use something along these lines:
This will create a 32 character identifier (a 128 bit hex number) that is extremely difficult to predict.
// no prefix
// works only in PHP 5 and later versions
$token = md5(uniqid());
// better, difficult to guess
$better_token = md5(uniqid(rand(), true));