Access GLOBAL variable in STATIC Method

Question

I am trying to access the global variable in a Static Method, But i am getting the Fatal Error:

Fatal error: Call to a member function prepare() on a non-object

Means my static variable can't hold the global variable, but this standard works with the normal method( without static ).

class Payment_Handler {


    private static $dbh;


    function __construct() { 
        global $dbh;

        self::$dbh = $dbh;
    }



    /**
     * Verify Secret Key
     * 
     * @param string $secret_key
     * @return boolean
     */
    static function verify_secret( $secret_key ) {
         // Do the stuff with self::$dbh
         $query = "............";
         $stmt = self::$dbh->prepare($query);
    }
} // End Class

I also tried over google but no luck. Please tell me what mistake i have done, and why it is not accessible by static variable?

you are mixing the static method with constructor make your function non static and with the object instance call the method something as $obj->verify_secret() so that during object instantiation property is set via __construct — Abhik Chakraborty
– Abhik Chakraborty, Commented Jun 12, 2014 at 11:38

Wrikken · Accepted Answer · 2014-06-12 11:39:13Z

2

If you've never instantiated a Payment_Handler object, it would indeed be NULL. I'd write a wrapper function instead of using self::$dbh directly:

class Payment_Handler {
    private static $dbh;
    function __construct() { 
        global $dbh;
        self::$dbh = $dbh;
    }
    static function getDBH(){
       if(is_nul(self::$dbh)) self::$dbh = $GLOBALS['dbh'];
       return self::$dbh;
    }
    static function verify_secret( $secret_key ) {
         $query = "............";
         $stmt = self::getDBH()->prepare($query);
    }
}

... or move away from the static method, and inject the proper requirements in instances.

answered Jun 12, 2014 at 11:39

Wrikken

70.8k8 gold badges99 silver badges136 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

ToBe Over a year ago

Working solution but please note the last sentence in this answer! Also note my answer which elaborates this a bit.

jogesh_pi Over a year ago

@ToBe yes i got these points during when i searched for solutions. But just want to know the way.

ToBe · Accepted Answer · 2014-06-12 11:49:22Z

1

Using a global Variable is ALLWAYS a bad idea, using static variables is often a bad idea.

You can give the $dbh object via the constructor to avoid globals:

class Payment_Handler {
    private $dbh;

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

    public function verify_secret( $secret_key ) {
        $query = "............";
        $stmt = $this->dbh->prepare($query);
    }
}

Or even better, use some kind of Dependency Injection:

class Payment_Handler {
    private $dbh;

    public function __construct(){}

    public function setConnector($dbh){
        $this->dbh = $dbh;
    }

    public function verify_secret( $secret_key ) {
        $query = "............";
        $stmt = $this->dbh->prepare($query);
    }
}

Why is globals bad?

Security issue. Your variable (database is even worse) is accessible from anywhere
State is uncontrolled. Other parts of code can change your variable without you knowing
Testing. It's very difficult to mock something that is global

Why is static bad?

Testing. It's very difficult to mock something that is global

Is there a drawback in those "good" samples?

No since PHP uses references internally wherever it can, you wont waste any memory and the performance won't drop by this very few lines of extra code.

(There are other reasons, whole books of them about this)

edited Jun 12, 2014 at 11:49

answered Jun 12, 2014 at 11:43

ToBe

2,6791 gold badge20 silver badges31 bronze badges

4 Comments

jogesh_pi Over a year ago

and how i initiate the Dependency Injection?

ToBe Over a year ago

In your main code, immediatly after you called the constructor, you call the setConnector method. Allways nice to have a central part of your code where all such classes are initialized and injected propery.

ToBe Over a year ago

Sorry, I left a static by mistake. These samples are not static. That might explain your question.

jogesh_pi Over a year ago

hmm, i was confused with the static in your examples. Thanks ;)

Collectives™ on Stack Overflow

Access GLOBAL variable in STATIC Method

2 Answers 2

2 Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related