<?php
Class Frog {
  protected static $colour1;
  public static $colour2;
  
  static function setColours($c1, $c2) { 
  	Frog::$colour1 = $c1;
  	Frog::$colour2 = $c2;
  }
  
  static function show() { 
  	echo "Frog: ".Frog::$colour1.", ".Frog::$colour2 ."\n";
  }
  
}

Class SpecialFrog extends Frog {
  public static $colour1;
  public static $colour2;
  
  static function setColours($c1, $c2) { 
  	SpecialFrog::$colour1 = $c1; //without patch, also sets Frog::$colour1! 
  	SpecialFrog::$colour2 = $c2;
  }
  
  static function show() { 
  	echo "SpecialFrog: ".SpecialFrog::$colour1.", ".SpecialFrog::$colour2 ."\n";
  }
  
}
Frog::setColours('green', 'green');
SpecialFrog::setColours('blue', 'blue');

Frog::show();
SpecialFrog::show();
?>

---- Output before patch (imho buggy) ----
Frog: blue, green
SpecialFrog: blue, blue

---- Output after patch ----
Frog: green, green
SpecialFrog: blue, blue