php在一个类中的函数之间共享变量

I'm new learner in PHP OOP, how can share or pass variable in between function within a class?

class Sample {

    public function One() {

         $var1 = 'abc';
         $var2 = 'xyz';

        return $var1;
    }

    public function Two() {

        $var3 = $var1.$var2;

        return $var3;
    }

}

Or is that possible to return multiple values?

thanks.

UPDATE

class Sample {

// This is how you declare class members
public $var1, $var2;

public function One() {

     // You use $this to refer class memebers
     $this->var1 = 'abc';
     $this->var2 = 'xyz';

    return $this->var1;
}

public function Two() {

    $var3 = $this->var1.$this->var2;

    return $var3;
}

}

$test = new Sample();
echo $test->Two();

I have test a provided example and it return blank in my page when calling function Two(), any idea?

Make the variables public variables, declared after class Sample { and they can be used anywhere inside the class.

declare variables inside class and use $this to access variables

class Sample {
    public $var1;
    public $var2;

    public function One() {
        $this->var1 = 'abc';
        $this->var2 = 'xyz';
        return $this->var1;
    }

    public function Two() {
        $var3 = $this->var1.$this->var2;
        return $var3;
    }
}

class Sample {

    // This is how you declare class members
    protected $var1, $var2;

    public function One() {

         // You use $this to refer class memebers
         $this->var1 = 'abc';
         $this->var2 = 'xyz';

        return $this->var1;
    }

    public function Two() {

        $var3 = $this->var1.$this->var2;

        return $var3;
    }

}