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1. Matt Van Andel
   Member
   Posted 1 year ago #

   I've created a custom class for a new plugin, instantiated it, and have no trouble using it in or out of functions.

   However, when I try to access a method of the instance within a function called by register_activation_hook(), I receive a PHP "Call to a member function on a non-object" error.

   Yes, I am declaring the instance as a global within the function.

   For example:

   class myClass{
      public function doStuff(){ return true; }
   }
   $myInstance = new myClass();
   register_activation_hook(__FILE__,'do_things');
   function doThings(){
      global $myInstance;
      $test = $myInstance->doStuff(); //non-object error
   }

   The above code SHOULD be valid, but returns a non-object error for doStuff when it's function is run by register_activation_hook.

   Ideas?

2. Matt Van Andel
   Member
   Posted 1 year ago #

   To answer my own question, I didn't realize that you could use ANY PHP callback style. On a whim, I simply changed my register_activation_hook to:

   register_activation_hook(__FILE__, $fpdb->install() );

   Bingo. It works.

3. Matt Van Andel
   Member
   Posted 1 year ago #

   One quick note for anyone stumbling on this, the above "fix" has scope resolution problems with WordPress.

   IMPORTANT NOTES:
   1. Only pass STATIC functions to hook callbacks (fixes scope problem) using the scope-resolution operator (::).
   2. Use only string-formatted callbacks (fixes WP 'expected callback' problem).

   The following is the only way to do this without running into problems (note that install() also had to be changed to a static function):

   register_activation_hook(__FILE__, 'myClass::install' );

4. Matt Van Andel
   Member
   Posted 1 year ago #

   Best Solution:

   Use array-formatted callbacks. For maximum compatibility, the above string-formatted static-method example should be converted to an array-formatted callback like this:

   register_activation_hook(__FILE__, array( 'myClass','install' );

   Here's why:
   String-formatted static-method callbacks are only supported in PHP 5.2+. To ensure maximum compatibility with earlier versions of PHP (I know, ugh), you should simply use array-formatted callbacks.

   The first array value is the class, the second is the method.

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