Duplicate code is one of the most pungent code smells. A rule that is often used is to re-structure code once it is duplicated in three or more places.
Common duplication problems, and corresponding solutions are:
Complex classes like FrmListHelper often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use FrmListHelper, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 6 | class FrmListHelper { | 
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| 7 | /**  | 
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| 8 | * The current list of items  | 
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| 9 | *  | 
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| 10 | * @since 2.0.18  | 
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| 11 | * @var array  | 
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| 12 | * @access public  | 
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| 13 | */  | 
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| 14 | public $items;  | 
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| 15 | |||
| 16 | /**  | 
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| 17 | * Various information about the current table  | 
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| 18 | *  | 
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| 19 | * @since 2.0.18  | 
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| 20 | * @var array  | 
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| 21 | * @access protected  | 
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| 22 | */  | 
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| 23 | protected $_args;  | 
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| 24 | |||
| 25 | /**  | 
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| 26 | * Various information needed for displaying the pagination  | 
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| 27 | *  | 
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| 28 | * @since 2.0.18  | 
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| 29 | * @var array  | 
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| 30 | */  | 
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| 31 | protected $_pagination_args = array();  | 
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| 32 | |||
| 33 | /**  | 
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| 34 | * The current screen  | 
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| 35 | *  | 
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| 36 | * @since 2.0.18  | 
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| 37 | * @var object  | 
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| 38 | * @access protected  | 
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| 39 | */  | 
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| 40 | protected $screen;  | 
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| 41 | |||
| 42 | /**  | 
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| 43 | * Cached bulk actions  | 
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| 44 | *  | 
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| 45 | * @since 2.0.18  | 
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| 46 | * @var array  | 
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| 47 | * @access private  | 
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| 48 | */  | 
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| 49 | private $_actions;  | 
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| 50 | |||
| 51 | /**  | 
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| 52 | * Cached pagination output  | 
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| 53 | *  | 
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| 54 | * @since 2.0.18  | 
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| 55 | * @var string  | 
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| 56 | * @access private  | 
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| 57 | */  | 
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| 58 | private $_pagination;  | 
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| 59 | |||
| 60 | /**  | 
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| 61 | * The view switcher modes.  | 
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| 62 | *  | 
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| 63 | * @since 2.0.18  | 
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| 64 | * @var array  | 
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| 65 | * @access protected  | 
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| 66 | */  | 
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| 67 | protected $modes = array();  | 
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| 68 | |||
| 69 | /**  | 
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| 70 | *  | 
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| 71 | * @var array  | 
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| 72 | */  | 
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| 73 | protected $params;  | 
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| 74 | |||
| 75 | /**  | 
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| 76 | * Stores the value returned by ->get_column_info()  | 
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| 77 | *  | 
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| 78 | * @var array  | 
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| 79 | */  | 
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| 80 | protected $_column_headers;  | 
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| 81 | |||
| 82 | protected $compat_fields = array( '_args', '_pagination_args', 'screen', '_actions', '_pagination' );  | 
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| 83 | |||
| 84 | protected $compat_methods = array( 'set_pagination_args', 'get_views', 'get_bulk_actions', 'bulk_actions',  | 
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| 
                                                                                                    
                        
                         | 
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| 85 | 'row_actions', 'months_dropdown', 'view_switcher', 'comments_bubble', 'get_items_per_page', 'pagination',  | 
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| 86 | 'get_sortable_columns', 'get_column_info', 'get_table_classes', 'display_tablenav', 'extra_tablenav',  | 
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| 87 | 'single_row_columns' );  | 
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| 88 | |||
| 89 | /**  | 
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| 90 | * Construct the table object  | 
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| 91 | */  | 
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| 92 | 	public function __construct( $args ) { | 
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| 127 | |||
| 128 | 	public function ajax_user_can() { | 
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| 131 | |||
| 132 | 	public function get_columns() { | 
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| 135 | |||
| 136 | 	public function display_rows() { | 
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| 143 | |||
| 144 | /**  | 
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| 145 | * Make private properties readable for backwards compatibility.  | 
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| 146 | *  | 
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| 147 | * @since 4.0.0  | 
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| 148 | * @access public  | 
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| 149 | *  | 
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| 150 | * @param string $name Property to get.  | 
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| 151 | * @return mixed Property.  | 
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| 152 | */  | 
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| 153 | 	public function __get( $name ) { | 
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| 158 | |||
| 159 | /**  | 
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| 160 | * Make private properties settable for backwards compatibility.  | 
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| 161 | *  | 
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| 162 | * @since 4.0.0  | 
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| 163 | * @access public  | 
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| 164 | *  | 
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| 165 | * @param string $name Property to check if set.  | 
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| 166 | * @param mixed $value Property value.  | 
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| 167 | * @return mixed Newly-set property.  | 
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| 168 | */  | 
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| 169 | 	public function __set( $name, $value ) { | 
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| 174 | |||
| 175 | /**  | 
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| 176 | * Make private properties checkable for backwards compatibility.  | 
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| 177 | *  | 
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| 178 | * @since 4.0.0  | 
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| 179 | * @access public  | 
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| 180 | *  | 
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| 181 | * @param string $name Property to check if set.  | 
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| 182 | * @return bool Whether the property is set.  | 
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| 183 | */  | 
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| 184 | 	public function __isset( $name ) { | 
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| 189 | |||
| 190 | /**  | 
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| 191 | * Make private properties un-settable for backwards compatibility.  | 
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| 192 | *  | 
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| 193 | * @since 4.0.0  | 
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| 194 | * @access public  | 
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| 195 | *  | 
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| 196 | * @param string $name Property to unset.  | 
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| 197 | */  | 
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| 198 | 	public function __unset( $name ) { | 
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| 203 | |||
| 204 | /**  | 
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| 205 | * Make private/protected methods readable for backwards compatibility.  | 
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| 206 | *  | 
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| 207 | * @since 4.0.0  | 
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| 208 | * @access public  | 
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| 209 | *  | 
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| 210 | * @param callable $name Method to call.  | 
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| 211 | * @param array $arguments Arguments to pass when calling.  | 
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| 212 | * @return mixed|bool Return value of the callback, false otherwise.  | 
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| 213 | */  | 
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| 214 | 	public function __call( $name, $arguments ) { | 
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| 220 | |||
| 221 | /**  | 
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| 222 | * Prepares the list of items for displaying.  | 
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| 223 | * @uses FrmListHelper::set_pagination_args()  | 
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| 224 | *  | 
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| 225 | * @since 2.0.18  | 
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| 226 | * @access public  | 
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| 227 | * @abstract  | 
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| 228 | */  | 
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| 229 | 	public function prepare_items() { | 
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| 232 | |||
| 233 | /**  | 
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| 234 | * An internal method that sets all the necessary pagination arguments  | 
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| 235 | *  | 
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| 236 | * @param array $args An associative array with information about the pagination  | 
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| 237 | * @access protected  | 
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| 238 | *  | 
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| 239 | * @param array|string $args  | 
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| 240 | */  | 
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| 241 | 	protected function set_pagination_args( $args ) { | 
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| 259 | |||
| 260 | /**  | 
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| 261 | * Access the pagination args.  | 
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| 262 | *  | 
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| 263 | * @since 2.0.18  | 
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| 264 | * @access public  | 
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| 265 | *  | 
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| 266 | * @param string $key Pagination argument to retrieve. Common values include 'total_items',  | 
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| 267 | * 'total_pages', 'per_page', or 'infinite_scroll'.  | 
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| 268 | * @return int Number of items that correspond to the given pagination argument.  | 
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| 269 | */  | 
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| 270 | 	public function get_pagination_arg( $key ) { | 
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| 277 | |||
| 278 | /**  | 
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| 279 | * Whether the table has items to display or not  | 
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| 280 | *  | 
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| 281 | * @since 2.0.18  | 
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| 282 | * @access public  | 
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| 283 | *  | 
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| 284 | * @return bool  | 
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| 285 | */  | 
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| 286 | 	public function has_items() { | 
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| 289 | |||
| 290 | /**  | 
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| 291 | * Message to be displayed when there are no items  | 
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| 292 | *  | 
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| 293 | * @since 2.0.18  | 
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| 294 | * @access public  | 
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| 295 | */  | 
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| 296 | 	public function no_items() { | 
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| 299 | |||
| 300 | /**  | 
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| 301 | * Display the search box.  | 
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| 302 | *  | 
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| 303 | * @since 2.0.18  | 
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| 304 | * @access public  | 
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| 305 | *  | 
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| 306 | * @param string $text The search button text  | 
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| 307 | * @param string $input_id The search input id  | 
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| 308 | */  | 
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| 309 | 	public function search_box( $text, $input_id ) { | 
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| 331 | |||
| 332 | /**  | 
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| 333 | * Get an associative array ( id => link ) with the list  | 
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| 334 | * of views available on this table.  | 
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| 335 | *  | 
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| 336 | * @since 2.0.18  | 
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| 337 | * @access protected  | 
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| 338 | *  | 
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| 339 | * @return array  | 
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| 340 | */  | 
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| 341 | 	protected function get_views() { | 
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| 344 | |||
| 345 | /**  | 
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| 346 | * Display the list of views available on this table.  | 
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| 347 | *  | 
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| 348 | * @since 2.0.18  | 
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| 349 | * @access public  | 
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| 350 | */  | 
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| 351 | 	public function views() { | 
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| 375 | |||
| 376 | /**  | 
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| 377 | * Get an associative array ( option_name => option_title ) with the list  | 
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| 378 | * of bulk actions available on this table.  | 
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| 379 | *  | 
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| 380 | * @since 2.0.18  | 
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| 381 | * @access protected  | 
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| 382 | *  | 
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| 383 | * @return array  | 
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| 384 | */  | 
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| 385 | 	protected function get_bulk_actions() { | 
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| 388 | |||
| 389 | /**  | 
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| 390 | * Display the bulk actions dropdown.  | 
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| 391 | *  | 
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| 392 | * @since 2.0.18  | 
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| 393 | * @access protected  | 
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| 394 | *  | 
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| 395 | * @param string $which The location of the bulk actions: 'top' or 'bottom'.  | 
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| 396 | * This is designated as optional for backwards-compatibility.  | 
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| 397 | */  | 
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| 398 | 	protected function bulk_actions( $which = '' ) { | 
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| 438 | |||
| 439 | /**  | 
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| 440 | * Get the current action selected from the bulk actions dropdown.  | 
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| 441 | *  | 
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| 442 | * @since 2.0.18  | 
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| 443 | * @access public  | 
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| 444 | *  | 
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| 445 | * @return string|false The action name or False if no action was selected  | 
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| 446 | */  | 
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| 447 | 	public function current_action() { | 
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| 459 | |||
| 460 | /**  | 
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| 461 | * Generate row actions div  | 
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| 462 | *  | 
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| 463 | * @since 2.0.18  | 
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| 464 | * @access protected  | 
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| 465 | *  | 
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| 466 | * @param array $actions The list of actions  | 
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| 467 | * @param bool $always_visible Whether the actions should be always visible  | 
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| 468 | * @return string  | 
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| 469 | */  | 
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| 470 | 	protected function row_actions( $actions, $always_visible = false ) { | 
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| 489 | |||
| 490 | /**  | 
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| 491 | * Display a monthly dropdown for filtering items  | 
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| 492 | *  | 
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| 493 | * @since 2.0.18  | 
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| 494 | * @access protected  | 
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| 495 | *  | 
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| 496 | * @global wpdb $wpdb  | 
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| 497 | * @global WP_Locale $wp_locale  | 
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| 498 | *  | 
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| 499 | * @param string $post_type  | 
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| 500 | */  | 
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| 501 | 	protected function months_dropdown( $post_type ) { | 
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| 562 | |||
| 563 | /**  | 
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| 564 | * Display a view switcher  | 
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| 565 | *  | 
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| 566 | * @since 2.0.18  | 
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| 567 | * @access protected  | 
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| 568 | *  | 
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| 569 | * @param string $current_mode  | 
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| 570 | */  | 
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| 571 | 	protected function view_switcher( $current_mode ) { | 
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| 591 | |||
| 592 | /**  | 
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| 593 | * Display a comment count bubble  | 
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| 594 | *  | 
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| 595 | * @since 2.0.18  | 
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| 596 | * @access protected  | 
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| 597 | *  | 
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| 598 | * @param int $post_id The post ID.  | 
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| 599 | * @param int $pending_comments Number of pending comments.  | 
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| 600 | */  | 
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| 601 | 	protected function comments_bubble( $post_id, $pending_comments ) { | 
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| 638 | |||
| 639 | /**  | 
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| 640 | * Get the current page number  | 
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| 641 | *  | 
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| 642 | * @since 2.0.18  | 
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| 643 | * @access public  | 
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| 644 | *  | 
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| 645 | * @return int  | 
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| 646 | */  | 
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| 647 | 	public function get_pagenum() { | 
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| 655 | |||
| 656 | /**  | 
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| 657 | * Get number of items to display on a single page  | 
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| 658 | *  | 
            ||
| 659 | * @since 2.0.18  | 
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| 660 | * @access protected  | 
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| 661 | *  | 
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| 662 | * @param string $option  | 
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| 663 | * @param int $default  | 
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| 664 | * @return int  | 
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| 665 | */  | 
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| 666 | 	protected function get_items_per_page( $option, $default = 20 ) { | 
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| 686 | |||
| 687 | /**  | 
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| 688 | * Display the pagination.  | 
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| 689 | *  | 
            ||
| 690 | * @since 2.0.18  | 
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| 691 | * @access protected  | 
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| 692 | *  | 
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| 693 | * @param string $which  | 
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| 694 | */  | 
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| 695 | 	protected function pagination( $which ) { | 
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| 805 | |||
| 806 | /**  | 
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| 807 | * Get a list of sortable columns. The format is:  | 
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| 808 | * 'internal-name' => 'orderby'  | 
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| 809 | * or  | 
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| 810 | * 'internal-name' => array( 'orderby', true )  | 
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| 811 | *  | 
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| 812 | * The second format will make the initial sorting order be descending  | 
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| 813 | *  | 
            ||
| 814 | * @since 2.0.18  | 
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| 815 | * @access protected  | 
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| 816 | *  | 
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| 817 | * @return array  | 
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| 818 | */  | 
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| 819 | 	protected function get_sortable_columns() { | 
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| 822 | |||
| 823 | /**  | 
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| 824 | * Gets the name of the default primary column.  | 
            ||
| 825 | *  | 
            ||
| 826 | * @since 4.3.0  | 
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| 827 | * @access protected  | 
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| 828 | *  | 
            ||
| 829 | * @return string Name of the default primary column, in this case, an empty string.  | 
            ||
| 830 | */  | 
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| 831 | 	protected function get_default_primary_column_name() { | 
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| 848 | |||
| 849 | /**  | 
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| 850 | * Gets the name of the primary column.  | 
            ||
| 851 | *  | 
            ||
| 852 | * @since 4.3.0  | 
            ||
| 853 | * @access protected  | 
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| 854 | *  | 
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| 855 | * @return string The name of the primary column.  | 
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| 856 | */  | 
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| 857 | 	protected function get_primary_column_name() { | 
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| 883 | |||
| 884 | /**  | 
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| 885 | * Get a list of all, hidden and sortable columns, with filter applied  | 
            ||
| 886 | *  | 
            ||
| 887 | * @since 2.0.18  | 
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| 888 | * @access protected  | 
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| 889 | *  | 
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| 890 | * @return array  | 
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| 891 | */  | 
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| 892 | 	protected function get_column_info() { | 
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| 938 | |||
| 939 | /**  | 
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| 940 | * Return number of visible columns  | 
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| 941 | *  | 
            ||
| 942 | * @since 2.0.18  | 
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| 943 | * @access public  | 
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| 944 | *  | 
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| 945 | * @return int  | 
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| 946 | */  | 
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| 947 | 	public function get_column_count() { | 
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| 952 | |||
| 953 | /**  | 
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| 954 | * Print column headers, accounting for hidden and sortable columns.  | 
            ||
| 955 | *  | 
            ||
| 956 | * @since 2.0.18  | 
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| 957 | * @access public  | 
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| 958 | *  | 
            ||
| 959 | * @staticvar int $cb_counter  | 
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| 960 | *  | 
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| 961 | * @param bool $with_id Whether to set the id attribute or not  | 
            ||
| 962 | */  | 
            ||
| 963 | 	public function print_column_headers( $with_id = true ) { | 
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| 1028 | |||
| 1029 | /**  | 
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| 1030 | * Display the table  | 
            ||
| 1031 | *  | 
            ||
| 1032 | * @since 2.0.18  | 
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| 1033 | * @access public  | 
            ||
| 1034 | */  | 
            ||
| 1035 | 	public function display() { | 
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| 1064 | |||
| 1065 | /**  | 
            ||
| 1066 | * Get a list of CSS classes for the list table table tag.  | 
            ||
| 1067 | *  | 
            ||
| 1068 | * @since 2.0.18  | 
            ||
| 1069 | * @access protected  | 
            ||
| 1070 | *  | 
            ||
| 1071 | * @return array List of CSS classes for the table tag.  | 
            ||
| 1072 | */  | 
            ||
| 1073 | 	protected function get_table_classes() { | 
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| 1076 | |||
| 1077 | /**  | 
            ||
| 1078 | * Generate the table navigation above or below the table  | 
            ||
| 1079 | *  | 
            ||
| 1080 | * @since 2.0.18  | 
            ||
| 1081 | * @access protected  | 
            ||
| 1082 | * @param string $which  | 
            ||
| 1083 | */  | 
            ||
| 1084 | 	protected function display_tablenav( $which ) { | 
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| 1102 | |||
| 1103 | /**  | 
            ||
| 1104 | * Extra controls to be displayed between bulk actions and pagination  | 
            ||
| 1105 | *  | 
            ||
| 1106 | * @since 2.0.18  | 
            ||
| 1107 | * @access protected  | 
            ||
| 1108 | *  | 
            ||
| 1109 | * @param string $which  | 
            ||
| 1110 | */  | 
            ||
| 1111 | 	protected function extra_tablenav( $which ) {} | 
            ||
| 1112 | |||
| 1113 | /**  | 
            ||
| 1114 | * Generate the tbody element for the list table.  | 
            ||
| 1115 | *  | 
            ||
| 1116 | * @since 2.0.18  | 
            ||
| 1117 | * @access public  | 
            ||
| 1118 | */  | 
            ||
| 1119 | 	public function display_rows_or_placeholder() { | 
            ||
| 1128 | |||
| 1129 | /**  | 
            ||
| 1130 | * Generates content for a single row of the table  | 
            ||
| 1131 | *  | 
            ||
| 1132 | * @since 2.0.18  | 
            ||
| 1133 | * @access public  | 
            ||
| 1134 | *  | 
            ||
| 1135 | * @param object $item The current item  | 
            ||
| 1136 | */  | 
            ||
| 1137 | 	public function single_row( $item ) { | 
            ||
| 1142 | |||
| 1143 | /**  | 
            ||
| 1144 | *  | 
            ||
| 1145 | * @param object $item  | 
            ||
| 1146 | * @param string $column_name  | 
            ||
| 1147 | */  | 
            ||
| 1148 | 	protected function column_default( $item, $column_name ) {} | 
            ||
| 1149 | |||
| 1150 | /**  | 
            ||
| 1151 | *  | 
            ||
| 1152 | * @param object $item  | 
            ||
| 1153 | */  | 
            ||
| 1154 | 	protected function column_cb( $item ) {} | 
            ||
| 1155 | |||
| 1156 | /**  | 
            ||
| 1157 | * Generates the columns for a single row of the table  | 
            ||
| 1158 | *  | 
            ||
| 1159 | * @since 2.0.18  | 
            ||
| 1160 | * @access protected  | 
            ||
| 1161 | *  | 
            ||
| 1162 | * @param object $item The current item  | 
            ||
| 1163 | */  | 
            ||
| 1164 | 	protected function single_row_columns( $item ) { | 
            ||
| 1208 | |||
| 1209 | /**  | 
            ||
| 1210 | * Generates and display row actions links for the list table.  | 
            ||
| 1211 | *  | 
            ||
| 1212 | * @since 4.3.0  | 
            ||
| 1213 | * @access protected  | 
            ||
| 1214 | *  | 
            ||
| 1215 | * @param object $item The item being acted upon.  | 
            ||
| 1216 | * @param string $column_name Current column name.  | 
            ||
| 1217 | * @param string $primary Primary column name.  | 
            ||
| 1218 | * @return string The row actions output. In this case, an empty string.  | 
            ||
| 1219 | */  | 
            ||
| 1220 | 	protected function handle_row_actions( $item, $column_name, $primary ) { | 
            ||
| 1223 | |||
| 1224 | /**  | 
            ||
| 1225 | * Handle an incoming ajax request (called from admin-ajax.php)  | 
            ||
| 1226 | *  | 
            ||
| 1227 | * @since 2.0.18  | 
            ||
| 1228 | * @access public  | 
            ||
| 1229 | */  | 
            ||
| 1230 | 	public function ajax_response() { | 
            ||
| 1257 | |||
| 1258 | /**  | 
            ||
| 1259 | * Send required variables to JavaScript land  | 
            ||
| 1260 | *  | 
            ||
| 1261 | * @access public  | 
            ||
| 1262 | */  | 
            ||
| 1263 | 	public function _js_vars() { | 
            ||
| 1274 | }  | 
            ||
| 1275 |