Introduction to four methods of generating unique IDs in php

There are many scenarios where unique IDs are used in work, such as temporary cache files, temporary variables, temporary security codes, etc.

The uniqid() function generates a unique ID based on the current time in microseconds. Since generating a unique ID is tied to a subtle time, the uniqueness of the generated ID is very reliable.

The generated unique ID returns a string that is 13 characters long by default. If combined with the MD5() function, the generated unique ID will be more reliable. This generated ID is the largest than a random ID. The advantage is that sorting can be achieved, especially for some values ​​that need to be stored in the database. Of course, random numbers can also be added here.

The following mainly introduces 4 methods of generating unique IDs:

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

Note: This method has There will be a certain probability of duplication

2. PHP built-in function uniqid()

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

  echo uniqid();
  echo uniqid();
  echo uniqid();
 OUTPUT:
    5a4b62dd4aeea
    5a4b62dd4aff7
    5a4b62dd4b069

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."

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3. Combine the md5() function to generate a unique ID

     echo md5(uniqid());
OUTPUT:
    0ac3d6e99b7f5290c93d730eaf9d7d94

4. Manually go Processing, the official case

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;
     }

returns similar results: E2DFFFB3-571E-6CFC-4B5C-9FEDAAF2EFD7

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