PHP uniqid()Functions

PHP Misc 参考手册PHP Misc Reference Manual

Examples

Generate a unique ID:

<?php
echo uniqid();
?>

Run Example »

Definition and Usage

The uniqid() function generates a unique ID based on the current time in microseconds.

Note:Since it is based on system time, the ID generated by this function is not optimal. To generate an absolutely unique ID, use themd5()function.

Syntax

uniqid(prefix,more_entropy)

Parameters Description
prefix Optional. Specifies a prefix for the unique ID. This parameter is useful if two scripts happen to generate IDs at the same microsecond.
more_entropy Optional. Specifies more entropy at the end of the return value. This makes the result more unique. When set to TRUE, the returned string is 23 characters. Default is FALSE, and the returned string is 13 characters.

Technical Details

Return Value: Returns the unique identifier as a string.
PHP Version: 4+
Changelog: In PHP 5.0,prefixthe parameter became optional.

In PHP 4.3.1,prefixthe 114-character length limit of the prefix was increased.

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