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                <?php  | 
            
                            
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                namespace Undefined\Stash;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * Theme setup  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 */  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                function setControllers()  | 
            
            
                                                                        
                            
            
                                    
            
            
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                { | 
            
            
                                                                        
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * Add the main language page id and name for the controller here  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    Controller::Instance()->setPages([  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        2 => "sample",  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    ]);  | 
            
            
                                                                        
                            
            
                                    
            
            
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                }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                add_action('init', __NAMESPACE__ . '\\setControllers'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                function setup()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // Enable features from Soil when plugin is activated  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // https://roots.io/plugins/soil/  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('soil-clean-up'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('soil-nav-walker'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('soil-nice-search'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('soil-jquery-cdn'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('soil-relative-urls'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // Make theme available for translation  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // Community translations can be found at https://github.com/roots/sage-translations  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    load_theme_textdomain('stash', get_template_directory() . '/lang'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // Enable plugins to manage the document title  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // http://codex.wordpress.org/Function_Reference/add_theme_support#Title_Tag  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('title-tag'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // Register wp_nav_menu() menus  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // http://codex.wordpress.org/Function_Reference/register_nav_menus  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    register_nav_menus([  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'primary_navigation' => __('Primary Navigation', 'stash') | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    ]);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // Enable post thumbnails  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // http://codex.wordpress.org/Post_Thumbnails  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // http://codex.wordpress.org/Function_Reference/set_post_thumbnail_size  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // http://codex.wordpress.org/Function_Reference/add_image_size  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('post-thumbnails'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // Enable post formats  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // http://codex.wordpress.org/Post_Formats  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('post-formats', ['aside', 'gallery', 'link', 'image', 'quote', 'video', 'audio']); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // Enable HTML5 markup support  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    // http://codex.wordpress.org/Function_Reference/add_theme_support#HTML5  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('html5', ['caption', 'comment-form', 'comment-list', 'gallery', 'search-form']); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    add_theme_support('menus'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                add_action('after_setup_theme', __NAMESPACE__ . '\\setup'); | 
            
            
                                                        
            
                                    
            
            
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The PSR-1: Basic Coding Standard recommends that a file should either introduce new symbols, that is classes, functions, constants or similar, or have side effects. Side effects are anything that executes logic, like for example printing output, changing ini settings or writing to a file.
The idea behind this recommendation is that merely auto-loading a class should not change the state of an application. It also promotes a cleaner style of programming and makes your code less prone to errors, because the logic is not spread out all over the place.
To learn more about the PSR-1, please see the PHP-FIG site on the PSR-1.