PHP简单生成通用唯一识别码（UUID）

UUID是由一组32位数的16进制数字所构成，是故UUID理论上的总数为16^32=2^128，约等于3.4 x 10^38。也就是说若每纳秒产生1兆个UUID，要花100亿年才会将所有UUID用完。UUID重复几率非常非常低，是故大可不必考虑重复冲突的问题。 像Java和Python都有专门库函数生成UUID，PHP也有第三方库可以用来生成UUID。 安装

我们使用composer来安装uuid库。 composer require ramsey/uuid 使用 首先require自动加载文件，然后直接调用UUID方法。

require 'vendor/autoload.php'; 
 
use Ramsey\Uuid\Uuid; 
use Ramsey\Uuid\Exception\UnsatisfiedDependencyException; 
 
try { 
 
    // Generate a version 1 (time-based) UUID object 
    $uuid1 = Uuid::uuid1(); 
    echo $uuid1->toString() . "\n"; // i.e. e4eaaaf2-d142-11e1-b3e4-080027620cdd 
 
    // Generate a version 3 (name-based and hashed with MD5) UUID object 
    $uuid3 = Uuid::uuid3(Uuid::NAMESPACE_DNS, 'helloweba.net'); 
    echo $uuid3->toString() . "\n"; // i.e. 11a38b9a-b3da-360f-9353-a5a725514269 
 
    // Generate a version 4 (random) UUID object 
    $uuid4 = Uuid::uuid4(); 
    echo $uuid4->toString() . "\n"; // i.e. 25769c6c-d34d-4bfe-ba98-e0ee856f3e7a 
 
    // Generate a version 5 (name-based and hashed with SHA1) UUID object 
    $uuid5 = Uuid::uuid5(Uuid::NAMESPACE_DNS, 'helloweba.net'); 
    echo $uuid5->toString() . "\n"; // i.e. c4a760a8-dbcf-5254-a0d9-6a4474bd1b62 
 
} catch (UnsatisfiedDependencyException $e) { 
 
    // Some dependency was not met. Either the method cannot be called on a 
    // 32-bit system, or it can, but it relies on Moontoast\Math to be present. 
    echo 'Caught exception: ' . $e->getMessage() . "\n"; 
 
}