3 ways to generate unique IDs in php_php tips

The editor checked many articles on the Internet about how to generate a unique ID in PHP, and found that there are many methods. I specially compiled this article to share with you the solution to how to generate a unique ID in PHP. I hope you like it.

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, which 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;
 }

The above are three ways to generate unique IDs in PHP. I hope it will be helpful to everyone's learning.