Come dice l'errore,ènecessaria un'istanza della classeper utilizzare $this. Ci sono almenotrepossibilità:

Renditutto statico

 class My_Plugin
{
    private static $var = 'foo';

    static function foo()
    {
        return self::$var; // never echo or print in a shortcode!
    }
}
add_shortcode( 'baztag', array( 'My_Plugin', 'foo' ) );
 

Ma questonon èpiù un vero OOP,solo uno spazio deinomi.

Creaprima un oggetto reale

 class My_Plugin
{
    private $var = 'foo';

    public function foo()
    {
        return $this->var; // never echo or print in a shortcode!
    }
}

$My_Plugin = new My_Plugin;

add_shortcode( 'baztag', array( $My_Plugin, 'foo' ) );
 

Questo ...funziona. Mati imbattiin alcuni problemi oscuri se qualcuno vuole sostituire lo shortcode.

Quindi aggiungi unmetodoperfornire l'istanza della classe:

 final class My_Plugin
{
    private $var = 'foo';

    public function __construct()
    {
        add_filter( 'get_my_plugin_instance', [ $this, 'get_instance' ] );
    }

    public function get_instance()
    {
        return $this; // return the object
    }

    public function foo()
    {
        return $this->var; // never echo or print in a shortcode!
    }
}

add_shortcode( 'baztag', [ new My_Plugin, 'foo' ] );
 

Ora,quando qualcuno vuole ottenere l'istanza dell'oggetto,deve solo scrivere:

 $shortcode_handler = apply_filters( 'get_my_plugin_instance', NULL );

if ( is_a( $shortcode_handler, 'My_Plugin ' ) )
{
    // do something with that instance.
}
 

Vecchia soluzione: crea l'oggettonellatua classe

 class My_Plugin
{
    private $var = 'foo';

    protected static $instance = NULL;

    public static function get_instance()
    {
        // create an object
        NULL === self::$instance and self::$instance = new self;

        return self::$instance; // return the object
    }

    public function foo()
    {
        return $this->var; // never echo or print in a shortcode!
    }
}

add_shortcode( 'baztag', array( My_Plugin::get_instance(), 'foo' ) );
 

As the error says you need an instance of the class to use $this. There are at least three possibilities:

Make everything static

class My_Plugin
{
    private static $var = 'foo';

    static function foo()
    {
        return self::$var; // never echo or print in a shortcode!
    }
}
add_shortcode( 'baztag', array( 'My_Plugin', 'foo' ) );

But that’s not real OOP anymore, just namespacing.

Create a real object first

class My_Plugin
{
    private $var = 'foo';

    public function foo()
    {
        return $this->var; // never echo or print in a shortcode!
    }
}

$My_Plugin = new My_Plugin;

add_shortcode( 'baztag', array( $My_Plugin, 'foo' ) );

This … works. But you run into some obscure problems if anyone wants to replace the shortcode.

So add a method to provide the class instance:

final class My_Plugin
{
    private $var = 'foo';

    public function __construct()
    {
        add_filter( 'get_my_plugin_instance', [ $this, 'get_instance' ] );
    }

    public function get_instance()
    {
        return $this; // return the object
    }

    public function foo()
    {
        return $this->var; // never echo or print in a shortcode!
    }
}

add_shortcode( 'baztag', [ new My_Plugin, 'foo' ] );

Now, when someone wants to get the object instance, s/he just has to write:

$shortcode_handler = apply_filters( 'get_my_plugin_instance', NULL );

if ( is_a( $shortcode_handler, 'My_Plugin ' ) )
{
    // do something with that instance.
}

Old solution: create the object in your class

class My_Plugin
{
    private $var = 'foo';

    protected static $instance = NULL;

    public static function get_instance()
    {
        // create an object
        NULL === self::$instance and self::$instance = new self;

        return self::$instance; // return the object
    }

    public function foo()
    {
        return $this->var; // never echo or print in a shortcode!
    }
}

add_shortcode( 'baztag', array( My_Plugin::get_instance(), 'foo' ) );

Puoi usarein questomodo,shortcode all'interno della classe

 class stockData{


    function __construct() {
        add_shortcode( 'your_shortcode_name', array( $this, 'showData' ) );
        //add_action('login_enqueue_scripts', array( $this,'my_admin_head'));
    }

    function showData(){
        return '<h1>My shortcode content</h1>' ;
    }
}

$object=new stockData();
 

Se desideri accedere al contenuto dello shortcode di un'altra classe.Puoifare così.

 class my_PluginClass {

  public function __construct( $Object ) {

    $test = add_shortcode( 'your_shortcode_name', array( $Object, 'your_method_name' ) );

  }

}

class CustomHandlerClass{

  public function your_method_name( $atts, $content ) {
     return '<h1>My shortcode content</h1>' ;
  }
}

$Customobject  = new CustomHandlerClass();
$Plugin         = new my_PluginClass( $Customobject );
 

You can use like this, shortcode inside the Class

class stockData{


    function __construct() {
        add_shortcode( 'your_shortcode_name', array( $this, 'showData' ) );
        //add_action('login_enqueue_scripts', array( $this,'my_admin_head'));
    }

    function showData(){
        return '<h1>My shortcode content</h1>' ;
    }
}

$object=new stockData();

If you want access shortcode content from another class. You can do like this.

class my_PluginClass {

  public function __construct( $Object ) {

    $test = add_shortcode( 'your_shortcode_name', array( $Object, 'your_method_name' ) );

  }

}

class CustomHandlerClass{

  public function your_method_name( $atts, $content ) {
     return '<h1>My shortcode content</h1>' ;
  }
}

$Customobject  = new CustomHandlerClass();
$Plugin         = new my_PluginClass( $Customobject );

Assicurati di creare un'istanza dellatua classeprima di usarla,ameno chetunon sia sicuro che debbaessere chiamata staticamente.Quando chiami unmetodoin modo statico,non usi alcunaistanzae quindinon ha accesso anessuna variabile ometodomembro.

Make sure that you make an instance of your class before using it unless you are sure it's supposed to be called statically. When you call a method statically, you don't use any instances and therefore it doesn't have access to any member variables or methods.