I'm new to OOP and I'm writing my first plugin. I want to check if the Facebook plugin has already been activated. If so, I want to skip some code:

class MyClass {
    function fb_js_sdk_setup() {
        // Check if Facebook plugin is activated 
        if ( class_exists( 'Facebook_WP' ) )
        // Continue if Facebook plugin is not active


My if (class_exists()) statement isn't working. Appreciate any advice and pointers. Thanks!

  • On which action do your create your instance? Make sure to wait until the Facebook plugin has started.
    – fuxia
    Commented Sep 6, 2012 at 3:56
  • @toscho oh, good point. My instance is attached to init which I guess is too early. When should I load it instead?
    – blogjunkie
    Commented Sep 6, 2012 at 3:59
  • 1
    wp_loaded maybe? I don’t know when the FB instance is created. Darshan’s advice is good.
    – fuxia
    Commented Sep 6, 2012 at 4:20

1 Answer 1


You should use is_plugin_active() method to check if a certain plugin is activated. The class Facebook_WP will still exists even you deactivate the plugin.


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