# Create GUID by random

### *當沒有的時候就自己生*

## 產出

直接貼上function

```php
/**
 * 取得隨機GUID字串, 依「$havedash」決定是否包含Dash
 * @param type $havedash 是否包含Dash
 * @return type GUID字串
 */
public static function CreateGUID($havedash) {

  if ($havedash) {
    $formatstring = '%04x%04x-%04x-%04x-%04x-%04x%04x%04x';
  } else {
    $formatstring = '%04x%04x%04x%04x%04x%04x%04x%04x';
  }

  return sprintf($formatstring,
          // 32 bits for "time_low"
          mt_rand(0, 0xffff), mt_rand(0, 0xffff),
          // 16 bits for "time_mid"
          mt_rand(0, 0xffff),
          // 16 bits for "time_hi_and_version",
          // four most significant bits holds version number 4
          mt_rand(0, 0x0fff) | 0x4000,
          // 16 bits, 8 bits for "clk_seq_hi_res",
          // 8 bits for "clk_seq_low",
          // two most significant bits holds zero and one for variant DCE1.1
          mt_rand(0, 0x3fff) | 0x8000,
          // 48 bits for "node"
          mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
  );
}
```


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