PHP 继承，组合，单模式，GUID,等混合实例

<?php
header("Content-type: text/html; charset=utf-8");
header('Access-Control-Allow-Origin:*'); 
$BiaDuak = '************';//定义变量  使用时 echo $BiaDuak;
define("accessKeyId","************");//定义常量 使用时 echo accessKeyId;
define("accessKeySecret","************");
define("endpoint","************");
//公共类
class DbHelp
{
  private  $servername="************.com:4065";
  private  $username="root" ;
  private  $password="w386161506";
  private  $dbname="allhelp_db";
  public  $conn;
  private static $_instance;
  public static function getInstance()    
  {    
    if(! (self::$_instance instanceof self) )   
    {    
        self::$_instance = new self();  
       
    }  
    return self::$_instance;    
  }
  private function __construct(){

      $this->conn=new mysqli($this->servername,$this->username,$this->password,$this->dbname); 
  }   
  private function __clone(){}
}
//公共函数
 function test_input($data)
 {
   $data = trim($data);
   $data = stripslashes($data);
   $data = htmlspecialchars($data);
   return $data;
 }
 function create_guid() {
    $charid = strtoupper(md5(uniqid(mt_rand(), true)));
    $hyphen = chr(45);// "-"
    $uuid = 
    substr($charid, 0, 8)
    .substr($charid, 8, 4)
    .substr($charid,12, 4)
    .substr($charid,16, 4)
    ;
    return $uuid;
}
function guid(){
    if (function_exists('com_create_guid')){
        return com_create_guid();
    }else{
        mt_srand((double)microtime()*10000);//optional for php 4.2.0 and up.
        $charid = strtoupper(md5(uniqid(rand(), true)));
        $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;
    }
}
function createguid() {
    $charid = strtoupper(md5(uniqid(mt_rand(), true)));
    $hyphen = chr(45);// "-"
    $uuid = 
    substr($charid, 0, 8).$hyphen
    .substr($charid, 8, 4).$hyphen
    .substr($charid,12, 4).$hyphen
    .substr($charid,16, 4).$hyphen
    .substr($charid,20,12)
    ;
    return $uuid;
}
//用于继承的基类
class DbHelpBase
{
  public  $servername;
  public  $username;
  public  $password;
  public  $dbname;
  public  $conn;
  public function DbHelpBase(){
    $this->servername="************:4065";
    $this->username="root" ;
    $this->password="w386161506";
    $this->dbname="allhelp_db";
    $this->conn=new mysqli($this->servername,$this->username,$this->password,$this->dbname); 
  }   
 public function test_input($data)
 {
   $data = trim($data);
   $data = stripslashes($data);
   $data = htmlspecialchars($data);
   return $data;
 }
 public function create_guid() {
    $charid = strtoupper(md5(uniqid(mt_rand(), true)));
    $hyphen = chr(45);// "-"
    $uuid = 
    substr($charid, 0, 8)
    .substr($charid, 8, 4)
    .substr($charid,12, 4)
    .substr($charid,16, 4)
    ;
    return $uuid;
}
}
//用于组合的类
class DbHelpField
{
  public  $servername;
  public  $username;
  public  $password;
  public  $dbname;
  public  $conn;
  private static $_instance;
  public static function getInstance()    
  {    
    if(! (self::$_instance instanceof self) )   
    {    
        self::$_instance = new self();  
       
    }  
    return self::$_instance;    
  }
  private function __construct(){
    $this->servername="************:4065";
    $this->username="root" ;
    $this->password="w386161506";
    $this->dbname="allhelp_db";
    $this->conn=new mysqli($this->servername,$this->username,$this->password,$this->dbname); 
  }   
  private function __clone(){}
 public function test_input($data)
 {
   $data = trim($data);
   $data = stripslashes($data);
   $data = htmlspecialchars($data);
   return $data;
 }
 public function create_guid() {
    $charid = strtoupper(md5(uniqid(mt_rand(), true)));
    $hyphen = chr(45);// "-"
    $uuid = 
    substr($charid, 0, 8)
    .substr($charid, 8, 4)
    .substr($charid,12, 4)
    .substr($charid,16, 4)
    ;
    return $uuid;
}
}
?>

<?php 
header("Content-type: text/html; charset=utf-8");
header('Content-Type: application/json');
header('Access-Control-Allow-Origin:*'); 
require "config.php";
class DataUser 
{
  private $conn;
  public function DataUser()
  { 
    $dbcontext=DbHelp::getInstance(); 
    $this->conn=$dbcontext->conn;
    if($this->conn->connect_error)
    {
     die("Connection failed: " . $conn->connect_error);
    } 
      
  }
  public function Query_alluser()
   {
    $sql = "SELECT * FROM users";
    $result = $this->conn->query($sql);
    $data =array();
     if ($result->num_rows > 0)
      {
          while($rowObject = $result->fetch_object())
          {
              $data[]=$rowObject;
          }
          $json = json_encode($data);//把数据转换为JSON数据.
          echo "{".'"Comment"'.":".$json."}";
      } 
     else 
     {
       echo "0 results";
     }
  }
}
echo "直接使用config.php中的类";
$t=new DataUser();
$t->Query_alluser();
echo "
";

class DataUser1 extends DbHelpBase
{
  public function Query_alluser()
   {
    $sql = "SELECT * FROM users";
    $result = $this->conn->query($sql);
    $data =array();
     if ($result->num_rows > 0)
      {
          while($rowObject = $result->fetch_object())
          {
              $data[]=$rowObject;
          }
          $json = json_encode($data);//把数据转换为JSON数据.
          echo "{".'"Comment"'.":".$json."}";
      } 
     else 
     {
       echo "0 results";
     }
  }
}
echo "继承config.php中的类";
$tt=new DataUser1();
echo $tt->servername;
echo $tt->create_guid();
echo $tt->Query_alluser();
echo "
";
class DataUser2 
{
  public $conn;
  public $formDbHelp;
  public function DataUser2()
  {
    $formDbHelp=DbHelpField::getInstance();
    $this->conn= $formDbHelp->conn;
  }
  public function Query_alluser()
   {
    $sql = "SELECT * FROM users";
    //$result = $this->formDbHelp->conn->query($sql);//PHP中好像不能三级访问古多定义一个$conn字段
    $result = $this->conn->query($sql);
    $data =array();
     if ($result->num_rows > 0)
      {
          while($rowObject = $result->fetch_object())
          {
              $data[]=$rowObject;
          }
          $json = json_encode($data);//把数据转换为JSON数据.
          echo "{".'"Comment"'.":".$json."}";
      } 
     else 
     {
       echo "0 results";
     }
  }
  public function CreateGuid()
  {
   echo $this->formDbHelp->create_guid();//错误
  }
}
echo "组合config.php中的类";
$ttt=new DataUser2();
echo $ttt->Query_alluser();
//echo $ttt->formDbHelp->create_guid();//错误
?>