Description:
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At the moment the only way (i know of) to determine if a function is called during shutdown by means of a register_shutdown function is to do a debug_backtrace which is a resource heavy function or to enable output buffering and check for PHP_OUTPUT_HANDLER_END which also uses resources for the output buffering

It would preferable to have a way to check if the script is in shutdown mode using a more lightweight function.

I took an implementation of a static constructor/destructor for a utility class as example but it would be usable for many other purposes

https://wiki.php.net/rfc/static_class_constructor considers the implementation of static constructors but also does not see the need for destructors. 
I agree that there is no need to create a standard implementation for a static destructor. However should you need it it would be really practical to detect that shutdown has started without allocating a lot of resources.



Test script:
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abstract class utilityClass{
 private static $_constructed = false;
 //seal the constructor to prevent creation even from subclasses
 final private function  __construct(){} 

 final public static function constructStatic(){
  if(self::$_constructed!==false) return;
  self::$_constructed = null;
  /* do construction here */
  self::$_constructed = true;
 }
 final public static function destructStatic(){ 
  if(self::$_constructed!==true) return;
  // I REALLY DON'T LIKE THE BELOW debug_backtrace call
  if(count(($bt=debug_backtrace()))>1 || isset($bt[0]['file']) || isset($bt[0]['line'])) return;
  $_constructed = null;
  /* do destruction here */

  $_constructed = false;
 }
}utilityClass::constructStatic();