Why are my constants not available outside my class?

Question

I'm developing a plugin and I try to use a class (following the method of another plugin). But I don't understand why my constants are not globally available. This is my code:

/*
Plugin Name: Some simple plugin
*/

  if (!session_id())
    session_start();

class myPluginClass {

  function __construct() {
    /* Set the constants needed by the plugin. */
    add_action( 'plugins_loaded', array( &$this, 'constants' ), 1 );
  }


  function constants() {
    $upload_dir = wp_upload_dir();

    define( 'SIMPLE_GALLERY_DIR', trailingslashit( str_replace('\\', '/', plugin_dir_path( __FILE__ )) ) );

    //This works and outputs http://.....
    echo SIMPLE_GALLERY_URL;
  }

}

$sg = new simpleGallery();
//This does not work and outputs SIMPLE_GALLERY_URL.
echo SIMPLE_GALLERY_URL;

The result of the above two is: SIMPLE_GALLERY_URLhttp://.....

This means that my last echo is executed before the class. Or is it?

constants() is attached to the plugins_loaded hook - could it be that this is executed after page is loaded?

Answer 1

Your constant is defined in the "plugins_loaded" action, but you are trying to access it before that action gets to be executed.