如何在php中访问它之外的构造函数的成员变量

I made the following example class

class a{

 function __construct(){
    $a =10;
    $b=9;
    }


}

$z=new a();

I would like to know how can I access $a and $b using the object(or by other means) to perform a single $a + $b addition. I know this can be done using the super global array but I would like to know are there any other methods to do this rather than declaring them global.

I know the code doesn't make much sense but doing it for example purposes

Make those variables properties instead:

class a
{
    public $a;
    public $b;

    public function __construct() {
        $this->a = 10;
        $this->b = 9;
    }
}

$z = new a();
echo $z->a;

Better yet though, abstract your operation into a function:

echo $z->addProperties();

// Inside a class
public function addProperties() {
    return $this->a + $this->b;
}

Later on, when you want to add a third property that you need to add to your other two (or even subtract or multiply by), then all you have to do is change your a class, and not any code that actually uses it.

In your example there are two local variables in the function. You should create class fields to access them via object:

class a {

    public $a;
    public $b;

    function __construct() {
        $this->a = 10;
        $this->b = 9;
    }
} 

$z = new a();

echo $z->a;

echo $z->b;

You can`t return in the cunstructor even if you do:

    class a{
     public $a;
     public $b;
     function __construct(){
        $this->a =10;
        $this->b=9;
        return 19;
     }
    }
$b = new a();
var_dump($b);

You would get an instance of a, thus you heve the alternatives: make a new method:

<?php
function add()
{
   return $this->a+$this->b;
}
?>

Or generate getter`s (for both) =>

<?php
function getA()
{
   return $this->a;
}
?>

Or declare them public and access them:

$z->a+$z->b;

It depends on you`r app architecture or restrictions you might have or want to impose

By name constructors are used for any initialization that the object may need before it is used. So if you do the way you are doing

function __construct(){
    $a =10;
    $b=9;
    }

The variables $a & $b scope are limited to the function __construct().

You may need $a & $b as class variable rather than the function something as

class a{
 public $a;
 public $b;
 function __construct(){
    $this->a =10;
    $this->b=9;
 }
}

$z=new a();
// access a & b as
$z->a ; $z->b

The constructor here will do the initialization job of the variables when you instantiate the object.