Detailed explanation of how to generate unique id in php

php generates a unique id. After checking online, there are many methods

1. md5(time() . mt_rand(1,1000000));

This method has certain The probability will be repeated

2. PHP built-in function uniqid()

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

There is a sentence in the w3school reference manual: "Because it is based on system time, the ID generated by this function is not optimal. If you need to generate an absolutely unique ID, please use the md5() function."

The following method returns similar results: 5DDB650F-4389-F4A9-A100-501EF1348872 For more information, please refer to my blog post: php example

function uuid() {if (function_exists ( 'com_create_guid' )) {return com_create_guid ();
    } else {mt_srand ( ( double ) microtime () * 10000 ); //optional for php 4.2.0 and up.随便数播种，4.2.0以后不需要了。$charid = strtoupper ( md5 ( uniqid ( rand (), true ) ) ); //根据当前时间（微秒计）生成唯一id.$hyphen = chr ( 45 ); // "-"$uuid = '' . //chr(123)// "{"substr ( $charid, 0, 8 ) . $hyphen . substr ( $charid, 8, 4 ) . $hyphen . substr ( $charid, 12, 4 ) . $hyphen . substr ( $charid, 16, 4 ) . $hyphen . substr ( $charid, 20, 12 );//.chr(125);// "}"return $uuid;
    }
}

com_create_guid() is a php self- The method of generating a unique ID seems to be gone after PHP5.
3. The official uniqid() reference manual has methods provided by users, and the results are similar: {E2DFFFB3-571E-6CFC-4B5C-9FEDAAF2EFD7}

public function create_guid($namespace = '') {     static $guid = '';$uid = uniqid("", true);$data = $namespace;$data .= $_SERVER['REQUEST_TIME'];$data .= $_SERVER['HTTP_USER_AGENT'];$data .= $_SERVER['LOCAL_ADDR'];$data .= $_SERVER['LOCAL_PORT'];$data .= $_SERVER['REMOTE_ADDR'];$data .= $_SERVER['REMOTE_PORT'];$hash = strtoupper(hash('ripemd128', $uid . $guid . md5($data)));$guid = '{' .   substr($hash,  0,  8) . 
            '-' .substr($hash,  8,  4) .
            '-' .substr($hash, 12,  4) .
            '-' .substr($hash, 16,  4) .
            '-' .substr($hash, 20, 12) .
            '}';return $guid;
  }

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