PHP uniqid() Function

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本文介绍了PHP uniqid()函数的使用方法，包括其参数、返回值特点及注意事项。通过实例演示了如何生成唯一标识符，并提供了提升ID唯一性的方法。此外，还探讨了与其他函数如md5()的对比，旨在帮助开发者高效地处理ID生成问题。

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Definition and Usage

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

Syntax

uniqid(prefix,more_entropy)

Parameter	Description
prefix	Optional. Specifies a prefix to the unique ID (useful if two scripts generate ids at exactly the same microsecond) Note: This parameter became optional in PHP 5
more_entropy	Optional. Specifies more entropy at the end of the return value. This will make the result more unique. When set to TRUE, the return string will be 23 characters. Default is FALSE, and the return string will be 13 characters long

Tips and Notes

Note: The generated ID from this function is not optimal, because it is based on the system time. To generate an extremely difficult to predict ID, use the md5() function (can be found in the String reference).