Cookbook problem

Im having some issues with this cookbook, not sure what's going wrong..It says this

displayRecipePHP Notice: Undefined variable: belgian_waffles in /home/treehouse/workspace/classe
s/cookbook.php on line 54
PHP Fatal error: Uncaught Error: Call to a member function getTitle() on null in /home/treehouse
/workspace/classes/render.php:26

I have looked at it 100 times, i dont get whats wrong here...

Here is my code from recipes.php

<?php class Recipe {

private $title;
private $ingredients = array();
private $instructions = array();
private $yield;
private $tag = array();
private $source = "Pontus Bolmér";

private $measurements = array (
  "tsp",
  "tspb",
  "cup",
  "oz",
  "lb",
  "fl oz",
  "pint",
  "quart",
  "gallon"
);


public function addIngredient ($item, $amount = null, $measure = null) {
    if($amount != null && !is_float($amount) && !is_int($amount)) {
      exit("The amount must be a float: " . gettype($amount) . " $amount give");
    }
  if($measure != null && !in_array(strtolower($measure), $this->measurements)) {
    exit("Please enter a valid measurement: " . implode(", ", $this->measurements));

  }
    $this->ingredients[] = array (
      "item" => ucwords($item),
      "amount" => $amount,
      "measure" => strtolower($measure)
    );

}

public function getIngredients() {
  return $this->ingredients;
}

public function addInstruction($string) {
  $this->instructions[] = $string;
}

public function getInstructions() {
  return $this->instructions;
}

public function addTag($tag) {
  $this->tags[] = strtolower($tag);
}


public function getTags() {
  return $this->tags;
}

public function setYield($yield) {
  $this->yield[] = $yield;
}

public function getYield() {
  return $this->yield;
}

public function setSource($source) {
  $this->source = ucwords($source);
}

public function getSource () {
  return $this->source;
}

public function setTitle($title){
   if(empty($title)) {
      $this->title = null;
    }
    else {
      $this->title = ucwords($title);
    } 
}


public function getTitle() {
  return $this->title;
}


public function __construct($title = null) {
  $this->setTitle($title);
} 


public function __toString() {
$output = "You are calling a " . __CLASS__ . " object with the title \"";
 $output .= $this->getTitle() . "\"";
 $output .= "\nIt is stored in " . basename(__FILE__) . " at " . __DIR__ .".";
 $output .= "\nThis display is from the line " .__LINE__ . " in method " . __METHOD__;
 $output .= "\nTHe following methods are available for  " . __CLASS__ . " objects: \n"; 
 $output .= implode("\n" ,get_class_methods(__CLASS__));
 return $output;
}

} ?>

and cookbook.php <?php include "classes/recipes.php"; include "classes/render.php"; include "classes/recipeCollection.php";

$cookbook = new RecipeCollection("Treehouse Recipes"); $cookbook->addRecipe($lemon_chicken); $cookbook->addRecipe($granola_muffins); $cookbook->addRecipe($belgian_waffles); $cookbook->addRecipe($pepper_casserole); $cookbook->addRecipe($lasagna);

$cookbook->addRecipe($dried_mushroom_ragout); $cookbook->addRecipe($rabbit_catalan); $cookbook->addRecipe($grilled_salmon_with_fennel); $cookbook->addRecipe($pistachio_duck); $cookbook->addRecipe($chili_pork); $cookbook->addRecipe($crab_cakes); $cookbook->addRecipe($beef_medallions); $cookbook->addRecipe($silver_dollar_cakes); $cookbook->addRecipe($french_toast); $cookbook->addRecipe($corn_beef_hash); $cookbook->addRecipe($granola); $cookbook->addRecipe($spicy_omelette); $cookbook->addRecipe($scones); var_dump($cookbook);

$recipe1 = new Recipe("My first recipe"); $recipe1->setSource = "Grandpa Pontus"; $recipe1->addIngredient("egg",1); $recipe1->addIngredient("flour",2, "cup");

$recipe2 = new Recipe("My second recipe"); $recipe2->setSource = "Grandpa Percy ";

$recipe1->addInstruction("This is my first instruction"); $recipe1->addInstruction("This is my second instruction");

$recipe1->addTag("Breakfast"); $recipe1->addTag("Main course");

$recipe1->setYield = ("6 servings");

echo $recipe1;

$test = new Render();

echo Render::displayRecipe($belgian_waffles);

?>

and render.php <?php class Render {

public function toString() { $output .= " "; $output .= "\nTHe following methods are available for " . __CLASS . " objects: \n"; $output .= implode("\n" ,get_class_methods(CLASS)); return $output; }

public static function listIngredients($ingredients) { $output = "" ; foreach($ingredients as $ing) { $output .= $ing['amount'] . " " .$ing['measure'] . " " .$ing['item'] ; $output .= "\n"; } return $output;

}

public static function displayRecipe($recipe) { //return $recipe->getTitle() . " by " . $recipe->getSource(); $output = " ";

 $output .= $recipe->getTitle() . " by " . $recipe->getSource();
 $output .= "\n\n";
 $output .= implode(", ", $recipe->getTags());
 $output .= self::listIngredients($recipe->getIngredients());
 $output .= "\n";


  $output .= "\n";

 $output .= implode("\n", $recipe->getInstructions());
 $output .= "\n";
 $output .= $recipe->getYield();
 return $output; 

}

}

?>

and recipeCollection.php

<?php class RecipeCollection {

private $title; private $recipes = array ();

public function __construct($title = null) { $this->setTitle($title); }

public function setTitle($title){ if(empty($title)) { $this->title = null; } else { $this->title = ucwords($title); } }

public function getTitle() { return $this->title; }

public function addRecipe ($recipe) { $this->recipe[] = $recipe; }

public function getRecipes() { return $this->recipes; }

}

?>