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 Give_DB 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 Give_DB, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 24 | abstract class Give_DB { | 
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| 25 | |||
| 26 | /**  | 
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| 27 | * The name of our database table  | 
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| 28 | *  | 
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| 29 | * @since 1.0  | 
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| 30 | * @access public  | 
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| 31 | *  | 
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| 32 | * @var string  | 
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| 33 | */  | 
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| 34 | public $table_name;  | 
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| 35 | |||
| 36 | /**  | 
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| 37 | * Set Minimum Index Length  | 
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| 38 | *  | 
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| 39 | * @since 2.0.1  | 
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| 40 | * @access public  | 
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| 41 | *  | 
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| 42 | * @var int  | 
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| 43 | */  | 
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| 44 | public $min_index_length = 191;  | 
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| 45 | |||
| 46 | /**  | 
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| 47 | * The version of our database table  | 
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| 48 | *  | 
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| 49 | * @since 1.0  | 
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| 50 | * @access public  | 
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| 51 | *  | 
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| 52 | * @var string  | 
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| 53 | */  | 
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| 54 | public $version;  | 
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| 55 | |||
| 56 | /**  | 
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| 57 | * The name of the primary column  | 
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| 58 | *  | 
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| 59 | * @since 1.0  | 
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| 60 | * @access public  | 
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| 61 | *  | 
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| 62 | * @var string  | 
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| 63 | */  | 
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| 64 | public $primary_key;  | 
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| 65 | |||
| 66 | /**  | 
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| 67 | * Class Constructor  | 
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| 68 | *  | 
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| 69 | * Set up the Give DB Class.  | 
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| 70 | *  | 
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| 71 | * @since 1.0  | 
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| 72 | * @access public  | 
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| 73 | */  | 
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| 74 | 	public function __construct() { | 
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| 79 | |||
| 80 | /**  | 
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| 81 | * Whitelist of columns  | 
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| 82 | *  | 
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| 83 | * @since 1.0  | 
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| 84 | * @access public  | 
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| 85 | *  | 
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| 86 | * @return array Columns and formats.  | 
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| 87 | */  | 
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| 88 | 	public function get_columns() { | 
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| 91 | |||
| 92 | /**  | 
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| 93 | * Default column values  | 
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| 94 | *  | 
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| 95 | * @since 1.0  | 
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| 96 | * @access public  | 
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| 97 | *  | 
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| 98 | * @return array Default column values.  | 
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| 99 | */  | 
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| 100 | 	public function get_column_defaults() { | 
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| 103 | |||
| 104 | /**  | 
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| 105 | * Retrieve a row by the primary key  | 
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| 106 | *  | 
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| 107 | * @since 1.0  | 
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| 108 | * @access public  | 
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| 109 | 52 | *  | 
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| 110 | 52 | * @param int $row_id Row ID.  | 
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| 111 | 52 | *  | 
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| 112 | 52 | * @return object  | 
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| 113 | */  | 
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| 114 | 	public function get( $row_id ) { | 
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| 125 | 2 | ||
| 126 | 2 | /**  | 
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| 127 | * Retrieve a row by a specific column / value  | 
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| 128 | *  | 
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| 129 | * @since 1.0  | 
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| 130 | * @access public  | 
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| 131 | *  | 
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| 132 | * @param int $column Column ID.  | 
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| 133 | * @param int $row_id Row ID.  | 
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| 134 | *  | 
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| 135 | * @return object  | 
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| 136 | 52 | */  | 
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| 137 | 52 | View Code Duplication | 	public function get_by( $column, $row_id ) { | 
            
| 150 | |||
| 151 | 52 | /**  | 
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| 152 | * Retrieve a specific column's value by the primary key  | 
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| 153 | *  | 
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| 154 | 52 | * @since 1.0  | 
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| 155 | 52 | * @access public  | 
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| 156 | *  | 
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| 157 | 52 | * @param int $column Column ID.  | 
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| 158 | * @param int $row_id Row ID.  | 
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| 159 | 52 | *  | 
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| 160 | * @return string Column value.  | 
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| 161 | 52 | */  | 
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| 162 | View Code Duplication | 	public function get_column( $column, $row_id ) { | 
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| 175 | |||
| 176 | 52 | /**  | 
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| 177 | * Retrieve a specific column's value by the the specified column / value  | 
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| 178 | 52 | *  | 
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| 179 | 1 | * @since 1.0  | 
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| 180 | * @access public  | 
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| 181 | *  | 
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| 182 | 52 | * @param int $column Column ID.  | 
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| 183 | 52 | * @param string $column_where Column name.  | 
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| 184 | 52 | * @param string $column_value Column value.  | 
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| 185 | *  | 
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| 186 | * @return string  | 
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| 187 | 52 | */  | 
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| 188 | 	public function get_column_by( $column, $column_where, $column_value ) { | 
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| 202 | |||
| 203 | 52 | /**  | 
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| 204 | * Insert a new row  | 
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| 205 | *  | 
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| 206 | * @since 1.0  | 
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| 207 | * @access public  | 
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| 208 | *  | 
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| 209 | * @param array $data  | 
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| 210 | * @param string $type  | 
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| 211 | *  | 
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| 212 | * @return int  | 
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| 213 | */  | 
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| 214 | 	public function insert( $data, $type = '' ) { | 
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| 257 | |||
| 258 | /**  | 
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| 259 | * Update a row  | 
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| 260 | *  | 
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| 261 | * @since 1.0  | 
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| 262 | * @access public  | 
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| 263 | *  | 
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| 264 | * @param int $row_id Column ID  | 
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| 265 | * @param array $data  | 
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| 266 | * @param string $where Column value  | 
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| 267 | *  | 
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| 268 | * @return bool  | 
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| 269 | */  | 
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| 270 | 	public function update( $row_id, $data = array(), $where = '' ) { | 
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| 304 | |||
| 305 | /**  | 
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| 306 | * Delete a row identified by the primary key  | 
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| 307 | *  | 
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| 308 | * @since 1.0  | 
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| 309 | * @access public  | 
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| 310 | *  | 
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| 311 | * @param int $row_id Column ID.  | 
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| 312 | *  | 
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| 313 | * @return bool  | 
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| 314 | */  | 
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| 315 | View Code Duplication | 	public function delete( $row_id = 0 ) { | 
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| 332 | |||
| 333 | /**  | 
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| 334 | * Check if the given table exists  | 
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| 335 | *  | 
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| 336 | * @since 1.3.2  | 
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| 337 | * @access public  | 
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| 338 | *  | 
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| 339 | * @param string $table The table name.  | 
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| 340 | *  | 
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| 341 | * @return bool If the table name exists.  | 
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| 342 | */  | 
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| 343 | 	public function table_exists( $table ) { | 
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| 351 | |||
| 352 | /**  | 
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| 353 | * Checks whether column exists in a table or not.  | 
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| 354 | *  | 
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| 355 | * @param string $column_name Name of the Column in Database Table.  | 
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| 356 | *  | 
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| 357 | * @since 1.8.18  | 
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| 358 | *  | 
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| 359 | * @see https://gist.github.com/datafeedr/54e89e07f87232fb055121bb766743fe  | 
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| 360 | *  | 
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| 361 | * @return bool  | 
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| 362 | */  | 
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| 363 | 	public function does_column_exist( $column_name ) { | 
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| 378 | |||
| 379 | /**  | 
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| 380 | * Check if the table was ever installed  | 
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| 381 | *  | 
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| 382 | * @since 1.6  | 
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| 383 | * @access public  | 
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| 384 | *  | 
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| 385 | * @return bool Returns if the customers table was installed and upgrade routine run.  | 
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| 386 | */  | 
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| 387 | 	public function installed() { | 
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| 390 | |||
| 391 | /**  | 
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| 392 | * Register tables  | 
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| 393 | *  | 
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| 394 | * @since 1.8.9  | 
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| 395 | * @access public  | 
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| 396 | */  | 
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| 397 | 	public function register_table() { | 
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| 403 | |||
| 404 | /**  | 
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| 405 | * Create table  | 
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| 406 | *  | 
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| 407 | * @since 1.8.9  | 
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| 408 | * @access public  | 
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| 409 | */  | 
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| 410 | 	public function create_table() { | 
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| 412 | |||
| 413 | |||
| 414 | /**  | 
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| 415 | * Given a ID, make sure it's a positive number, greater than zero before inserting or adding.  | 
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| 416 | *  | 
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| 417 | * @access private  | 
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| 418 | * @since 2.0  | 
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| 419 | *  | 
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| 420 | * @param int $id A passed ID.  | 
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| 421 | *  | 
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| 422 | * @return int|bool The normalized log ID or false if it's found to not be valid.  | 
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| 423 | */  | 
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| 424 | 	public function sanitize_id( $id ) { | 
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| 443 | |||
| 444 | /**  | 
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| 445 | * Handle switch blog on multi-site  | 
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| 446 | *  | 
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| 447 | * @since 2.0.4  | 
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| 448 | *  | 
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| 449 | * @access public  | 
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| 450 | *  | 
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| 451 | * @param $new_blog_id  | 
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| 452 | * @param $prev_blog_id  | 
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| 453 | */  | 
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| 454 | 	public function handle_switch_blog( $new_blog_id, $prev_blog_id ) { | 
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| 474 | }  | 
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| 475 |