WordPress – add_menu_page, [ $this, ‘function’ ] not a valid class name or object

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I would like to understand why I cannot use [ $this, ‘function’ ] within it’s own class.

This works:

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init.php 

if ( is_admin() )
{
    require ( dirname ( __FILE__ ) . '/inc/admin/Admin.php' );
    add_action('admin_menu', ['MangoAdmin', 'adminMenu'] );
}

/inc/admin/Admin.php – Version 1 (working) 

<?php namespace Mango;

class Admin
{
    public function adminMenu()
    {
    //this is the main item for the menu
    add_menu_page(
        'Mango Settings', //page title
        'Mango Settings', //menu title
        'manage_options', //capabilities
        'mango-settings', //menu slug
        [ 'MangoAdmin', 'settingsPage' ] // LOOK HERE *******
    );
    }

    public function settingsPage()
    {
        echo 'This is a test';
    }
}

/inc/admin/Admin.php – Version 2 (not working) 

<?php namespace Mango;

class Admin
{
    public function adminMenu()
    {
    //this is the main item for the menu
    add_menu_page(
        'Mango Settings', //page title
        'Mango Settings', //menu title
        'manage_options', //capabilities
        'mango-settings', //menu slug
        [ $this, 'settingsPage' ] // LOOK HERE *******
    );
    }

    public function settingsPage()
    {
        echo 'This is a test';
    }
}

Error Message: Warning: call_user_func_array() expects parameter 1 to be a valid callback, first array member is not a valid class name or object in /.../wp-includes/plugin.php on line 429

I don’t really understand why I cannot register [ $this, 'settingsPage' ] with the add_menu_page hook. Surely the working version 1 is needlesly creating a 2nd copy of the MangoAdmin class?

Can anybody shed some light on this for me please?

Post Views: 1

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1 comment

  1. Maybe a little late for an answer, but it probably would help others too;

    If the function is a member of a class within the plugin it should be
    referenced as array( $this, ‘function_name’ )

    http://codex.wordpress.org/Function_Reference/add_menu_page

    class Admin
{
    public function adminMenu()
    {
    //this is the main item for the menu
     add_menu_page(
        'Mango Settings', //page title
        'Mango Settings', //menu title
        'manage_options', //capabilities
        'mango-settings', //menu slug
        array( $this, 'settingsPage' ) // LOOK HERE *******
    );
    }

    public function settingsPage()
    {
        echo 'This is a test';
    }
}