Use PHP uniqid function to generate unique ID, phpuniqid function id_PHP tutorial

Use PHP uniqid function to generate unique ID, phpuniqid function id

The application scenarios for generating unique ID are very common, such as temporary cache file names, temporary variables, temporary security codes, etc., uniqid () function generates a unique ID based on the current time in microseconds. Since generating a unique ID is tied to microsecond time, the uniqueness of the ID is very reliable.

The generated unique ID returns a string that is 13 strings long by default. If the prefix of the unique ID is not defined, it can return up to 23 strings long. If combined with the md5() function, the generated unique ID will be more reliable. The biggest advantage of this generated ID is that it can be sorted, especially for some values ​​that need to be stored in the database.

1. Function prototype

string uniqid ( [string prefix [, bool more_entropy]] )

You can define the prefix and length of the unique ID

Second, version compatible

PHP 3, PHP 4, PHP 5

3. Basic usage and examples of functions

1, generate a unique ID

<&#63;php 
echo uniqid(); 
&#63;> 

2, combined with the md5() function to generate a unique ID

<&#63;php 
echo md5(uniqid()); 
&#63;> 

Output: dfbc5c8c6438de075da28b3c8a413fd0

3, generate multiple unique IDs, since it is measured in microseconds

<&#63;php 
echo uniqid(); 
echo uniqid(); 
echo uniqid(); 
&#63;> 

Output:

4bfd0e375396b
4bfd0e3753981
4bfd0e3753983

Judging from the generated results, unique IDs are sortable.
Generating a unique ID using the uniqid() function can be used to generate both a temporary ID and a permanent unique ID (storage database).

ps: Several solutions to generate unique IDs in php

The editor below has compiled three solutions for you, the details are as follows:

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

This method has a certain probability of duplication

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

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 PHP’s own method of generating a unique ID. It seems to be no longer available 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;
 }