Call to undefined function

Question

I wan't to include his instant messaging app in Wordpress. I can't find the issue even with the multiple same questions in the multiple forums.

My code : intrachat.php

<?php
/*
Plugin Name: Intrachat
Plugin URI: *************
Description: Chattez en temps réel sur votre intranet
Version: 0.1
Author: *********
License: GPL2
*/

class Intrachat_Plugin
{
    
    public function __construct()
    {
        include_once plugin_dir_path( __FILE__ ).'/page_title.php';
        include_once plugin_dir_path( __FILE__ ).'/chat.php';
        new IC_Page_Title();
        $chat = new IC_Chat();
        
    }
}

new Intrachat_Plugin();
?>

chat.php :

<?php

class IC_Chat {

    public function __construct()
    {
        add_action( 'init', ic_show_chat_bar());
    }

    public function ic_show_chat_bar() {    
        if(is_user_logged_in()){
            echo "<script>alert(\"Connecté\")</script>"; 
        }   
    }
    
    
}

?>

My problem :

Fatal error: Call to undefined function ic_show_chat_bar() in /var/www/vhosts/dev/html/wp-content/plugins/Intrachat/chat.php on line 7

EDIT :

Trying this :

<?php

class IC_Chat {

    public function __construct()
    {
        add_action( 'init', array($this, 'ic_show_chat_bar()'));
    }

    public function ic_show_chat_bar() {    
        if(is_user_logged_in()){
            echo "<script>alert(\"Connecté\")</script>"; 
        }   
    }
    
    
}

?>

Still same error.

Answer 1

The problem, as pointed out in the php error, is on line 7 of the "chat.php" file:

add_action( 'init', ic_show_chat_bar());

This line has two problems:

1. The correct syntax for a valid callback function should be without the parenthesis and wrapped in single quotes.
2. Since the function is declared inside a php class, it won't be accesible to add_action unless we pass the class instance itself as an argument. Since the function is not static, we can use $this to pass the current instance.

Thus, the correct syntax in this case would be:

add_action( 'init', array( $this, 'ic_show_chat_bar' ) );

I recommend visiting the code reference for add_action() and also reading the user contributed notes at the bottom, where several examples of how to work with actions when using a class can be found.