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Generate a unique ID uniqid
(PHP 4, PHP 5)
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.
Parameters
prefixCan 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. Ifmore_entropyisTRUE, it will be 23 characters.more_entropyIf 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 the unique identifier, as a string.
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));
?>Changelog
Version Description 5.0.0 The prefixparameter was made optional.4.3.1 The limit of 114 characters long for prefixwas raised.Notes
CautionThis function does not generate cryptographically secure tokens, in fact without being passed any additional parameters the return value is little different from microtime(). If you need to generate cryptographically secure tokens use openssl_random_pseudo_bytes().
Note:
Under Cygwin, the
more_entropymust be set toTRUEfor this function to work.