Complex classes like Attributes 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 Attributes, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 8 | class Attributes implements AttributesInterface  | 
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| 9 | { | 
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| 10 | /**  | 
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| 11 | * Stores the attribute data.  | 
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| 12 | *  | 
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| 13 | * @var \drupol\htmltag\AttributeInterface[]  | 
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| 14 | */  | 
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| 15 | private $storage = array();  | 
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| 16 | |||
| 17 | /**  | 
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| 18 |      * {@inheritdoc} | 
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| 19 | */  | 
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| 20 | 26 | public function __construct(array $attributes = array())  | 
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| 24 | |||
| 25 | /**  | 
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| 26 |      * {@inheritdoc} | 
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| 27 | */  | 
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| 28 | 26 | public function import($attributes = array())  | 
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| 36 | |||
| 37 | /**  | 
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| 38 |      * {@inheritdoc} | 
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| 39 | */  | 
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| 40 | 7 | public function set($name, $value = null)  | 
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| 49 | |||
| 50 | /**  | 
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| 51 |      * {@inheritdoc} | 
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| 52 | */  | 
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| 53 | 2 | public function offsetGet($name)  | 
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| 61 | |||
| 62 | /**  | 
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| 63 |      * {@inheritdoc} | 
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| 64 | */  | 
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| 65 | 1 | public function offsetSet($name, $value = null)  | 
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| 69 | |||
| 70 | /**  | 
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| 71 |      * {@inheritdoc} | 
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| 72 | */  | 
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| 73 | 1 | public function offsetUnset($name)  | 
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| 77 | |||
| 78 | /**  | 
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| 79 |      * {@inheritdoc} | 
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| 80 | */  | 
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| 81 | 2 | public function offsetExists($name)  | 
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| 85 | |||
| 86 | /**  | 
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| 87 |      * {@inheritdoc} | 
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| 88 | */  | 
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| 89 | 14 | public function append($key, $value = '')  | 
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| 104 | |||
| 105 | /**  | 
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| 106 |      * {@inheritdoc} | 
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| 107 | */  | 
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| 108 | 2 | public function remove($key, $value = '')  | 
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| 120 | |||
| 121 | /**  | 
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| 122 |      * {@inheritdoc} | 
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| 123 | */  | 
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| 124 | 2 | public function delete($name)  | 
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| 132 | |||
| 133 | /**  | 
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| 134 |      * {@inheritdoc} | 
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| 135 | */  | 
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| 136 | 1 | public function without($key)  | 
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| 142 | |||
| 143 | /**  | 
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| 144 |      * {@inheritdoc} | 
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| 145 | */  | 
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| 146 | 1 | public function replace($key, $value, $replacement)  | 
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| 163 | |||
| 164 | /**  | 
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| 165 |      * {@inheritdoc} | 
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| 166 | */  | 
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| 167 | 1 | public function merge(array $data = array())  | 
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| 183 | |||
| 184 | /**  | 
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| 185 |      * {@inheritdoc} | 
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| 186 | */  | 
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| 187 | 1 | public function exists($key, $value = null)  | 
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| 199 | |||
| 200 | /**  | 
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| 201 |      * {@inheritdoc} | 
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| 202 | */  | 
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| 203 | 3 | public function contains($key, $value)  | 
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| 211 | |||
| 212 | /**  | 
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| 213 |      * {@inheritdoc} | 
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| 214 | */  | 
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| 215 | 7 | public function __toString()  | 
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| 219 | |||
| 220 | /**  | 
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| 221 |      * {@inheritdoc} | 
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| 222 | */  | 
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| 223 | 15 | public function render()  | 
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| 229 | |||
| 230 | /**  | 
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| 231 |      * {@inheritdoc} | 
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| 232 | */  | 
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| 233 | 2 | public function toArray()  | 
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| 250 | |||
| 251 | /**  | 
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| 252 |      * {@inheritdoc} | 
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| 253 | */  | 
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| 254 | 1 | public function getStorage()  | 
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| 258 | |||
| 259 | /**  | 
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| 260 |      * {@inheritdoc} | 
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| 261 | */  | 
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| 262 | 1 | public function getIterator()  | 
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| 266 | |||
| 267 | /**  | 
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| 268 |      * {@inheritdoc} | 
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| 269 | */  | 
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| 270 | 1 | public function count()  | 
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| 274 | |||
| 275 | /**  | 
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| 276 | * Returns all storage elements as an array.  | 
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| 277 | *  | 
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| 278 | * @return \drupol\htmltag\AttributeInterface[]  | 
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| 279 | * An associative array of attributes.  | 
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| 280 | */  | 
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| 281 | 16 | private function prepareValues()  | 
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| 312 | |||
| 313 | /**  | 
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| 314 | * Normalize a value.  | 
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| 315 | *  | 
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| 316 | * @param mixed $value  | 
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| 317 | * The value to normalize.  | 
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| 318 | *  | 
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| 319 | * @return array  | 
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| 320 | * The value normalized.  | 
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| 321 | */  | 
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| 322 | 18 | private function normalizeValue($value)  | 
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| 326 | |||
| 327 | /**  | 
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| 328 | * Todo.  | 
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| 329 | *  | 
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| 330 | * @param mixed $value  | 
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| 331 | * Todo.  | 
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| 332 | *  | 
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| 333 | * @return array  | 
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| 334 | * The array, flattened.  | 
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| 335 | */  | 
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| 336 | 18 | private function ensureFlatArray($value)  | 
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| 380 | |||
| 381 | /**  | 
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| 382 | * Todo.  | 
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| 383 | *  | 
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| 384 | * @param mixed $value  | 
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| 385 | * Todo.  | 
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| 386 | *  | 
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| 387 | * @return string  | 
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| 388 | * A string.  | 
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| 389 | */  | 
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| 390 | 20 | private function ensureString($value)  | 
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| 419 | }  | 
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| 420 |