在PHP中如何从另一个类调用属性的方法

Question

I got into a little issue while trying to do some Php object.

I have these classes :

class a
{
    public $day;

    function __construct(){
        $this->day = new DateTime("now");
    }
}

class b
{
    public $test;

    function __construct(){
        $this->test = new a()
    }
    function myFunc(){
        $this->test->day->format('Y-m-d');
    }
}

I get this error when calling myFunc:

Fatal error: Call to a member function format() on a non-object

How could I call from class 'b' the method of an object attribute contained in a class 'a'?

EDIT : Okay so I actually made the above code simpler than what I really have in order to post it here and doing so the error didn't make it through... Here is a code closer to what I have and that displays the error I was talking about

<?php
date_default_timezone_set('America/Chicago');
class a
{
    public $day;
}

function __construct($day = "now")
{
    $this->day = new DateTime($day);
}

class b
{
public $test;

function __construct(){
    $this->test = new a();
    }   
function myFunc(){
    echo $this->test->day->format("Y-m-d");
    }   
}
$bclass = new b();
$bclass->myFunc();
?>

This is exactly what I get when executing it:

 ( ! ) Fatal error: Call to a member function format() on a non-object in C:\\wamp\\www\\axpo\\newPHPClass.php on line 21 Call Stack # Time Memory Function Location 1 0.0023 256080 {main}( ) ..\\newPHPClass.php:0 2 0.0024 257128 b->myFunc( ) ..\\newPHPClass.php:25 

I don't understand why it isn't working... I know it's surely something stupid and basic but I just don't see it...

Answer 1

you are missing a semicolon at

$this->test = new a();

and you either have to return or echo the value inside myFunc() of class b to be able to do something with it. Take a look at this:

<?php
class a
{
    public $day;

    function __construct(){
        $this->day = new DateTime("now");
    }
}

class b
{
    public $test;

    function __construct(){
        $this->test = new a(); // Added a semicolon !
    }
    public function myFunc(){
       return $this->test->day->format('Y-m-d'); // Return the value
    }
}

$b= new b();
echo $b->myFunc(); // echo the returned value from the function

?>

Answer 2

The problem with the new code is that you close the class definition after defining public $day

class a { public $day; } // Class gets closed with the last curly bracket !

So the __constructor function isnt called at all ! Delete the curly bracket after "public $day;" and add it after the definition of the __construct function. Then it should work !

Lucian