PHP References: An understanding

Question

I have seen in my journey to creaitng and building some of my php applications, the & symbol within front of vars, = and class names.

I understand that these are PHP References, but the docs i have seen and looked at seem to just not explain it in a way that i understand or confusing. How can you explain the following examples that i have seen to make them more understandable.

  public static function &function_name(){...}

  $varname =& functioncall();

  function ($var, &$var2, $var3){...}

Much appreciated

Answer 1

Let's say you have two functions

$a = 5;
function withReference(&$a) {
    $a++;
}
function withoutReference($a) {
    $a++;
}

withoutReference($a);
// $a is still 5, since your function had a local copy of $a
var_dump($a);
withReference($a);
// $a is now 6, you changed $a outside of function scope
var_dump($a);

So, passing argument by reference allows function to modify it outside of the function scope.

Now second example.

You have a function which returns a reference

class References {
    public $a = 5;
    public function &getA() {
        return $this->a;
    }
}

$references = new References;
// let's do regular assignment
$a = $references->getA();
$a++;
// you get 5, $a++ had no effect on $a from the class
var_dump($references->getA());

// now let's do reference assignment
$a = &$references->getA();
$a++;
// $a is the same as $reference->a, so now you will get 6
var_dump($references->getA());

// a little bit different
$references->a++;
// since $a is the same as $reference->a, you will get 7
var_dump($a);