uniqid
(PHP 4, PHP 5, PHP 7)
uniqid — Generate a unique ID
Description
string uniqid ([ string $prefix = "" [, bool $more_entropy = false ]] )Gets a prefixed unique identifier based on the current time in microseconds.
Caution
This function does not generate cryptographically secure values, and should not be used for cryptographic purposes. If you need a cryptographically secure value, consider using random_int(), random_bytes(), or openssl_random_pseudo_bytes() instead.
Warning
This function does not guarantee uniqueness of return value. Since most systems adjust system clock by NTP or like, system time is changed constantly. Therefore, it is possible that this function does not return unique ID for the process/thread. Use more_entropy to increase likelihood of uniqueness.
Parameters
prefix
Can be useful, for instance, if you generate identifiers simultaneously on several hosts that might happen to generate the identifier at the same microsecond.
With an empty prefix, the returned string will be 13 characters long. If more_entropy is TRUE, it will be 23 characters.
more_entropy
If set to TRUE, uniqid() will add additional entropy (using the combined linear congruential generator) at the end of the return value, which increases the likelihood that the result will be unique.
Return Values
Returns timestamp based unique identifier as a string.
Warning
This function tries to create unique identifier, but it does not guarantee 100% uniqueness of return value.
Examples
Example #1 uniqid() Example
<?php
/*?A?uniqid,?like:?4b3403665fea6?*/
printf("uniqid():?%s\r\n",?uniqid());
/*?We?can?also?prefix?the?uniqid,?this?the?same?as?
?*?doing:
?*
?*?$uniqid?=?$prefix?.?uniqid();
?*?$uniqid?=?uniqid($prefix);
?*/
printf("uniqid('php_'):?%s\r\n",?uniqid('php_'));
/*?We?can?also?activate?the?more_entropy?parameter,?which?is?
?*?required?on?some?systems,?like?Cygwin.?This?makes?uniqid()
?*?produce?a?value?like:?4b340550242239.64159797
?*/
printf("uniqid('',?true):?%s\r\n",?uniqid('',?true));
?>Notes
Note: Under Cygwin, the
more_entropymust be set toTRUEfor this function to work.
← time_sleep_until
unpack →
? 1997–2017 The PHP Documentation GroupLicensed under the Creative Commons Attribution License v3.0 or later.
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