Revert "Remove the various ways to set a callable"

This reverts commit ddbf7ba.

Author: UsingSession

reference/funchand/functions/register-tick-function.xml

@@ -64,8 +64,19 @@ function my_function($param) {
     echo "Tick callback function called with param: $param\n";
 }
 
+// Class with a method
+class my_class {
+    public function my_method($param) {
+        echo "Tick callback method called with param: $param\n";
+    }
+}
+
 // using a function as the callback
 register_tick_function('my_function', true);
+
+// using an object->method
+$object = new my_class();
+register_tick_function(array($object, 'my_method'), true);
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     </programlisting>