When I Execute in Console Nothing Happens.

<?php
include("classes/recipe.php");
include("classes/render.php");
include("inc/allrecipes.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);

$breakfast = new RecipeCollection("Breakfeasts");
foreach ($cookbook->filterByTag("breakfeast") as $recipe) {
  $breakfast->addRecipe($recipe); 

}


echo Render::listRecipes($breakfast->getRecipeTitles());
//echo Render::displayRecipe($lemon_chicken);

<?php

class Render
{
    public function __toString()
    {
        $output = "The 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)
    {
        $output = "";
        $output .= $recipe->getTitle() . " by " . $recipe->getSource();
        $output .= "\n";
        $output .= implode(", ",$recipe->getTags());
        $output .= "\n\n";
        $output .= self::listIngredients($recipe->getIngredients());
        $output .= "\n";
        $output .= implode("\n", $recipe->getInstructions());
        $output .= "\n";
        $output .= $recipe->getYield();
        return $output;
    }

    public static function listRecipes($titles)
    {
        return implode("\n",$titles);
    }
}

<?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->recipes[] = $recipe;
  }
  public function getRecipes()
  {
    return $this->recipes;
  }
  public function getRecipeTitles() 
  {
    $titles = array();
    foreach ($this->recipes as $recipe) {
     $titles[] = $recipe->getTitle(); 
         }
    return $titles;
  }
  public function filterByTag($tag)
  {
      $taggedRecipes = array();
      foreach($this->recipes as $recipe) {
       if (in_array(strtolower($tag), $recipe->getTags())){
        $taggedRecipes[] = $recipe;

       }
      }
   return $taggedRecipes;
  }
}

<?php

class Recipe 
{
  private $title;
  private $ingredients = array();
  private $instructions = array();
  private $yield;
  private $tag = array();
  private $source; 
  private $measurements = array(
    "tsp",
    "tbsp",
    "cup",
    "oz",
    "lb",
    "fl oz",
    "pint",
    "quart",
    "gallon"
  );
  public function __construct($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 form line" . __LINE__ . "in method" . __METHOD__;
    $output.="\nThe following methods are available for objects on this class:\n" ; 
    $output.= implode("\n",get_class_methods(__CLASS__));
    return $output;
  }
  public function setTitle($title)
  { 
    if(empty($title)) {
      $this->title = null;
    } else{
     $this->title = ucwords($title);
                                }
  }
  public function getTitle()
  { 
    return $this->title;
  }
  public function addIngredient($item, $amount=null, $measure = null)
  { if ($amount != null && !is_float($amount) && !is_int($amount)) {
    exit("The amount must be a float: " . gettype($amount) . "Amount Given");
  }
   if ($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)
    {
      $this->yield = ucwords($yield);
    }
    public function getYield()
    {
      return $this->yield;
    }
  public function setSource($source) 
  {
    $this->source = ucwords($source);
  }
  public function getSource() 
  {
    return $this->source;
  }
  public function displayRecipe() 
  {
    return $this->title . " by " . $this->source;
  }

}