Share variables between functions in PHP without using globals

Question

I have a class for interacting with a memcache server. I have different functions for inserting, deleting and retrieving data. Originally each function made a call to

Answer 1

You should use dependency injection. The singleton pattern and static constructs are considered bad practice because they essentially are globals (and for good reason -- they cement you to using whatever class you instantiate as opposed to some other).

Here is something like what you should do in order to have easy maintenance.

class MemCache {
    protected $memcache;

    public function __construct(){
        $this->memcache = memcache_connect();
    }
}

class Client {
    protected $MemCache;

    public function __construct( MemCache $MemCache ){
        $this->MemCache = $MemCache;
    }

    public function getMemCache(){
        return $this->MemCache;
    }
}

$MemCache = new MemCache();
$Client = new Client($MemCache);
$MemCache1 = $Client->getMemCache();

// $MemCache and $MemCache1 are the same object. 
// memcache_connect() has not been called more than once.

Answer 2

Pass in the MC instance:

class abc
{
    function __construct($mc) {
        $this->mc = $mc;
    }
}    
class def
{
    function __construct($mc) {
        $this->mc = $mc;
    }
}

$mc = new cache_class;
$abc = new abc($mc);

etc.

Answer 3

I would code another class using singleton pattern for getting the only instance of memcache. Like this -

class MemCache 
{ 
  private static $instance = false;   
  private function __construct() {}

  public static function getInstance()
  { 
    if(self::$instance === false)
    { 
      self::$instance = memcache_connect(); 
    } 

    return self::$instance; 
  } 
}

and usage -

$mc = MemCache::getInstance();
memcache_get($mc, ...)
...

Answer 4

I think you're looking for static properties here.

class mc {
    private static $instance;

    public static function getInstance() {
        if (self::$instance== null) {
            self::$instance= new self;
        }
        return self::$instance;
    }

    private function __construct() {
        $this->mem = memcache_connect(...);
    }
}

This implements a basic singleton pattern. Instead of constructing the object call mc::getInstance(). Have a look at singletons.