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                <?php  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * The home page controller.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                class HomeController extends SiteController  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    private static $popular_blacklist = array(  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'silverstripe/framework',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'silverstripe/cms',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'silverstripe/sqlite3',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'silverstripe/postgresql',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'silverstripe-themes/simple'  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    );  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public static $allowed_actions = array(  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'index'  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    );  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function index()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return $this->renderWith(array('Home', 'Page')); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function Title()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return 'Home';  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function Link()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return Director::baseURL();  | 
            
                            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param int $limit  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return DataList|SS_Limitable default to Relative addons  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function PopularAddons($limit = 10)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return self::RelativePopularAddons($limit);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param int $limit  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return DataList|SS_Limitable List sorted by absolute downloads  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public static function AbsolutePopularAddons($limit = 10)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return Addon::get()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            ->sort('Downloads', 'DESC') | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            ->exclude('Name', self::config()->popular_blacklist) | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            ->limit($limit);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                    public static function RelativePopularAddons($limit = 10)  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    { | 
            
            
                                                                        
                            
            
                                    
            
            
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                        $addons = Addon::get()  | 
            
            
                                                                        
                            
            
                                    
            
            
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                            ->exclude(array('Name' => self::config()->popular_blacklist)); | 
            
            
                                                                        
                            
            
                                    
            
            
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                        $list = ArrayList::create($addons->toArray());  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        /** @var ArrayList $addons */  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        $addons = $list->sort('relativePopularity DESC'); | 
            
            
                                                                        
                            
            
                                    
            
            
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                        $addons = $addons->limit($limit);  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        foreach ($addons as $addon) { | 
            
            
                                                                        
                            
            
                                    
            
            
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                            $addon->Score = $addon->relativePopularityFormatted() . ' per day';  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        return $addons;  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function NewestAddons($limit = 10)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return Addon::get()->sort('Released', 'DESC')->limit($limit); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function RandomAddons($limit = 10)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return Addon::get()->sort(DB::getConn()->random(), 'DESC')->limit($limit);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function NewestVersions($limit = 10)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return AddonVersion::get()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            ->filter('Development', false) | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            ->sort('Released', 'DESC') | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            ->limit($limit);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function ChartData()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $chartData = array();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $list = ArrayList::create(array());  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $sqlQuery = new SQLQuery();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $sqlQuery->setFrom('Addon'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $sqlQuery->setSelect('DATE(Created) as Created'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $sqlQuery->selectField('COUNT(*)', 'CountInOneDay'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $sqlQuery->addWhere('"Created" >= DATE_SUB(NOW(), INTERVAL 30 DAY)'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $sqlQuery->addGroupBy('DATE(Created)'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $result = $sqlQuery->execute();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        if (count($result)) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            foreach ($result as $row) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                $date = date('j M Y', strtotime($row['Created'])); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                if (!isset($chartData[$date])) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                    $chartData[$date] = $row['CountInOneDay'];  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        if (count($chartData)) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            foreach ($chartData as $x => $y) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                $list->push(ArrayData::create(array(  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                    'XValue' => $x,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                    'YValue' => $y  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                )));  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return $list;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                }  | 
            
            
                                                        
            
                                    
            
            
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.