Summary of methods for generating unique numeric IDs in php_php tips

Regarding the problem of generating a unique digital ID, do you need to use rand to generate a random number, and then query the database to see if there is such a number? This seems a bit time-consuming. Is there any other way?

Of course not, there are actually two ways to solve it.

1. If you only use PHP and not a database, then the timestamp random number is the best method and it does not repeat;

2. If you need to use a database, you also need to associate some other data with this ID. Then give the id of the table in the MySQL database an AUTO_INCREMENT (auto-increment) attribute. Each time a piece of data is inserted, the id automatically increases to 1, and then uses mysql_insert_id() or LAST_INSERT_ID() to return the auto-incremented id.

Of course, there is already a ready-made solution to this problem. Using the php uuid extension can perfectly solve this problem. This extension can generate a unique complete digital signature. .

If you don’t use composer, please refer to https://github.com/lootils/uuid,

If your project is based on composer, please refer to https://github.com/ramsey/uuid

I won’t move the specific source code, friends can just take it down and use it directly

PHP generated unique identifier code example:

< &#63;
//生成唯一标识符
//sha1()函数， "安全散列算法（SHA1）"
function create_unique() {
$data = $_SERVER['HTTP_USER_AGENT'] . $_SERVER['REMOTE_ADDR']
.time() . rand();
return sha1($data);
//return md5(time().$data);
//return $data;
}
&#63;>

PHP generates unique identifier function description and examples

< &#63;
$newhash = create_unique();
echo $newhash;
&#63;>

Let me share one more with you

/*
 * 信号量(Semaphore)。
 * 这是一个包装类，用于解决不同平台下对“信号量”的不同实现方式。
 * 目前这个类只是象征性的，在 Windows 平台下实际是空跑（并没有真的实现互斥）。
 */
class SemWrapper
{
  private $hasSemSupport;
  private $sem;
  const SEM_KEY = 1;

  public function __construct()
  {
    $this->hasSemSupport = function_exists( 'sem_get' );
    if ( $this->hasSemSupport ) {
      $this->sem = sem_get( self::SEM_KEY );
    }
  }

  public function acquire() {
    if ( $this->hasSemSupport ) {
      return sem_acquire( $this->sem );
    }
    return true;
  }

  public function release() {
    if ( $this->hasSemSupport ) {
      return sem_release( $this->sem );
    }
    return true;
  }
}

/*
 * 顺序号发生器。
 */
class SeqGenerator
{
  const SHM_KEY = 1;

  /**
   * 对顺序号发生器进行初始化。
   * 仅在服务器启动后的第一次调用有效，此后再调用此方法没有实际作用。
   * @param int $start 产生顺序号的起始值。
   * @return boolean 返回 true 表示成功。
   */
  static public function init( $start = 1 )
  {
    // 通过信号量实现互斥，避免对共享内存的访问冲突
    $sw = new SemWrapper;
    if ( ! $sw->acquire() ) {
      return false;
    }

    // 打开共享内存
    $shm_id = shmop_open( self::SHM_KEY, 'n', 0644, 4 );
    if ( empty($shm_id) ) {
      // 因使用了 'n' 模式，如果无法打开共享内存，可以认为该共享内存已经创建，无需再次初始化
      $sw->release();
      return true;
    }

    // 在共享内存中写入初始值
    $size = shmop_write( $shm_id, pack( 'L', $start ), 0 );
    if ( $size != 4 ) {
      shmop_close( $shm_id );
      $sw->release();
      return false;
    }

    // 关闭共享内存，释放信号量
    shmop_close( $shm_id );
    $sw->release();
    return true;
  }

  /**
   * 产生下一个顺序号。
   * @return int 产生的顺序号
   */
  static public function next()
  {
    // 通过信号量实现互斥，避免对共享内存的访问冲突
    $sw = new SemWrapper;
    if ( ! $sw->acquire() ) {
      return 0;
    }

    // 打开共享内存
    $shm_id = shmop_open( self::SHM_KEY, 'w', 0, 0 );
    if ( empty($shm_id) ) {
      $sw->release();
      return 0;
    }

    // 从共享内存中读出顺序号
    $data = shmop_read( $shm_id, 0, 4 );
    if ( empty($data) ) {
      $sw->release();
      return 0;
    }

    $arr = unpack( 'L', $data );
    $seq = $arr[1];

    // 把下一个顺序号写入共享内存
    $size = shmop_write( $shm_id, pack( 'L', $seq + 1 ), 0 );
    if ( $size != 4 ) {
      $sw->release();
      return 0;
    }

    // 关闭共享内存，释放信号量
    shmop_close( $shm_id );
    $sw->release();
    return $seq;
  }
}

$a = SeqGenerator::init( time() );
var_dump($a);

for ( $i=0; $i < 10; $i++ ) {
  $seq = SeqGenerator::next();
  var_dump($seq);
}

Okay, let’s stop here today, I hope it will be helpful to everyone learning PHP