可以在新类中从mysqli扩展并将其用作静态吗？

Question

What I want to do is this:

class DB extends mysqli {
 ...
}

DB :: connect( ... );

DB :: query( "SELECT * FROM myDB" );

class AnotherClass {
  function helloWorld()
  {
     DB :: query( "SELECT * FROM withoutUsingGlobalKeyword" );
  }
}

function functions()
{
    DB :: query( "SELECT * FROM withoutUsingGlobalKeyword" );
}

The point of this question is to avoid the use of the 'global' keyword like:

global $mysqli;
$mysqli = new mysqli( ... );

class AnotherClass {
   function helloWorld()
   {
      global $mysqli;
      $mysqli->query( "SELECT * FROM IDontWantToUseGlobalKeyword" );
   }
}

function functions()
{
    global $mysqli;
    $mysqli->query( "SELECT * FROM IDontWantToUseGlobalKeyword" );
}

A solution for this is to declare the mysqli variable in the $_ENV array, but I don't want to use $_ENV to manage the MYSQLI, I want to use a static class like DB (Is that possible?)

Answer 1

This falls under the composition over inheritance . With the example you provided it would be much better to jsut pass the class a mysql object.

Class DB {
    protected $mysqli;
    function __construct( Mysqli $mysqli ) {
        $this->mysqli = $mysqli;
    }
    function helloWorld() {
        $this->mysqli->query( "SELECT * FROM IDontWantToUseGlobalKeyword" );
    }
}

$db = new DB( new mysqli(...) );
$db->helloWorld();

Your examples don't seem to require any inheritance.

Answer 2

After of all, I found a solution:

global $mysqli;
$mysqli = new mysqli( ... );

class DB  {
  public static function getConnection()
  {
     global $mysqli;
     return $mysqli;
  }
 ...
}



$mysqli->query( "SELECT * FROM myDB" );

class AnotherClass {  
  function helloWorld()
  {
     $db = DB :: getConnection();
     $db->query( "SELECT * FROM withoutUsingGlobalKeyword" );
  }
}

class DBAccess {
   public $db;
   function __construct()
   {
      $this->db = DB :: getConnection();
   }
}

class MultipleMethodDBSupport extends DBAccess {
   function __construct()
   {
       parent :: __construct();
   }

   function m1()
   {
      $this->db->query( "SELECT * FROM withoutUsingGlobalKeyword" );
   }

   function m2()
   {
      $this->db->query( "SELECT * FROM withoutUsingGlobalKeyword" );
   }
}

function functions()
{
    $db = DB :: getConnection();
    $db->query( "SELECT * FROM withoutUsingGlobalKeyword" );
}