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What is the difference between Php $ this & # 8594; $ propery_name and $ this-> propery_name

    $protected_property_name = '_'.$name;
    if(property_exists($this, $protected_property_name)){
        return $this->$protected_property_name;
    }

I am following an Object Oriented Programming tutorial, however, the instructor came up with a new code structure that I have not seen before, without clearly explaining why he did it. if you notice in the if () statement $ this -> $ protected_property_name has two $ signs, one for $ this and the other for $ protected_property_name should usually be $ this-> protected_property_name without a dollar sign in the protected_property_name variable. when I tried to remove the $ sign from the protected_property_name variable an error was thrown. the complete code looks like this

class Addrress{

  protected $_postal_code;

  function __get($name){
    if(!$this->_postal_code){
        $this->_postal_code = $this->_postal_code_guess();
    }

    //Attempt to return protected property by name  

    $protected_property_name = '_'.$name;
    if(property_exists($this, $protected_property_name)){
        return $this->$protected_property_name;
    }

    //Unable to access property; trigger error.
    trigger_error('Undefined property via __get:() '. $name);
    return NULL;        
}
}
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2 answers


This is an example class:

class Example {
    public $property_one = 1;
    public $property_two = 2;
}

You can see the difference in the following codes:



$example = new Example();
echo $example->property_one; //echo 1

$other_property = 'property_two';
echo $example->$other_property; // equal to $example->property_two and echo 2

Non-OOP example:

$variable_one = 100;
$variable_name = 'variable_one';
echo $$variable_name; // equal to echo $variable_one and echo 100
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Suppose we have a class

class Test {
   public $myAttr = 1;
}
var $x = new Test();

We can access a public attribute like $ x-> myAttr.



What if we have an attribute name in a variable like

$var = 'myAttr';

We can access the attribute value using $ x -> $ var

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