CODEWITHSUNDEEP
phpoop
theminer3746
theminer3746

Reputation: 918

Warning: Creating default object from empty value that should have been set

I'm trying to setup a mailing system for my first time. I'm using PHPMailer but ,since there are quite a lot of thing to set I wrap that in another class to make it easier for myself, I've got this Warning: Creating default object from empty value. My code is like.

class Mail{
public $m;

public function __construct(){
    $m = new PHPMailer;

    //config like isSMTP, Host, Username, Password etc.
    }
}

but when is call method like

    public function subject($subject){
         $m->Subject = $subject;
    }

and var_dump($m->Subject); I'll get Warning: Creating default object from empty value

My questions are

1.Why that error is occurring?

  1. Is this the best way of doing this sort of thing, or is there any better way?(I heard that instantiate an object inside another object isn't a good practice)

Upvotes: 0

Views: 2112

Answers (2)

slevy1
slevy1

Reputation: 3832

One of the most important aspects of PHP's OOP support is the $this pseudo-variable. It evaluates as an object's address in memory, which is why it's not really a variable since an object's address may be invariable. Without $this, a method is unable to access the objects properties or other methods.

If a variable $whatever appears in a method, nothing indicates that the variable has any relationship to the object; it's just a variable. The only way for PHP to access a property (or another method) is by means of $this, since the pseudo-variable provides the object's address. If the property exists, it will be an offset from that address.

Note, you can do some powerful things with $this. For example, if you return that variable in a method, you can set up method chaining, as follows:

class test {
    public $m;

    public function setM( $num ){
        $this->m = $num;
        return $this;
    }
    public function getM(){
        return $this->m;
    }
}
echo (new test())->setM(15)->getM(); // 15

Live demo here

There appears to be a discrepancy between what the manual says about $this:

$this is a reference to the calling object ... (see http://php.net/manual/en/language.oop5.basic.php)

and PHP's internal source code which indicates that the pseudo-variable is actually a pointer (See PHP's internals here), despite the fact that PHP presents itself as not having pointers!

Whatever the true nature of $this, clearly it plays a critical role for a method to read and set member variables or to invoke another method.

Upvotes: 0

jeroen
jeroen

Reputation: 91744

If you want to access your class property in your methods, you need to use $this:

public $m;

public function __construct(){
    $this->m = new PHPMailer;

    //config like isSMTP, Host, Username, Password etc.
}
...
public function subject($subject){
     $this->m->Subject = $subject;
}

Upvotes: 3

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