Complex classes like ArrayHelper 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 ArrayHelper, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 15 | class ArrayHelper  | 
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| 16 | { | 
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| 17 | /**  | 
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| 18 | * Builds a map (key => value) from a multidimensional array or an array of objects.  | 
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| 19 | *  | 
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| 20 | * @param $array  | 
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| 21 | * @param string|\Closure $from  | 
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| 22 | * @param string|\Closure $to  | 
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| 23 | * @param string|\Closure|null $group  | 
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| 24 | * @return array  | 
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| 25 | */  | 
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| 26 | public static function map($array, $from, $to, $group = null)  | 
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| 41 | |||
| 42 | /**  | 
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| 43 | * Merges two or more arrays into one recursively.  | 
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| 44 | *  | 
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| 45 | * @param $a  | 
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| 46 | * @param $b  | 
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| 47 | * @return array  | 
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| 48 | */  | 
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| 49 | public static function merge($a, $b)  | 
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| 72 | |||
| 73 | /**  | 
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| 74 | * Checks if the given array contains the specified key.  | 
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| 75 | *  | 
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| 76 | * @param $key  | 
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| 77 | * @param $array  | 
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| 78 | * @param bool $caseSensitive  | 
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| 79 | * @return bool  | 
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| 80 | */  | 
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| 81 | public static function keyExists($key, $array, $caseSensitive = true)  | 
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| 95 | |||
| 96 | /**  | 
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| 97 | * Indexes an array according to a specified key.  | 
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| 98 | *  | 
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| 99 | * @param $array  | 
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| 100 | * @param $key  | 
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| 101 | * @return array  | 
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| 102 | */  | 
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| 103 | public static function index($array, $key)  | 
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| 113 | |||
| 114 | /**  | 
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| 115 | * Converts an object or an array of objects into an array.  | 
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| 116 | *  | 
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| 117 | * @param $object  | 
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| 118 | * @param array $properties  | 
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| 119 | * @param bool $recursive  | 
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| 120 | * @return array  | 
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| 121 | */  | 
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| 122 | public static function toArray($object, $properties = [], $recursive = true)  | 
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| 161 | |||
| 162 | /**  | 
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| 163 | * Retrieves the value of an array element or object property with the given key or property name.  | 
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| 164 | *  | 
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| 165 | * @param $array  | 
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| 166 | * @param $key  | 
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| 167 | * @param null $default  | 
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| 168 | * @return mixed|null  | 
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| 169 | */  | 
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| 170 | public static function getValue($array, $key, $default = null)  | 
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| 201 | |||
| 202 | /**  | 
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| 203 | * Removes an item from an array and returns the value.  | 
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| 204 | *  | 
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| 205 | * @param $array  | 
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| 206 | * @param $key  | 
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| 207 | * @param null $default  | 
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| 208 | * @return mixed|null  | 
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| 209 | */  | 
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| 210 | public static function remove(&$array, $key, $default = null)  | 
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| 221 | |||
| 222 | /**  | 
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| 223 | * Returns the first value in a given array.  | 
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| 224 | *  | 
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| 225 | * @param $arr  | 
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| 226 | * @return mixed  | 
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| 227 | */  | 
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| 228 | public static function getFirstValue($arr)  | 
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| 241 | |||
| 242 | |||
| 243 | /**  | 
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| 244 | * Finds matching values from two arrays  | 
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| 245 | *  | 
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| 246 | * @param array $keys  | 
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| 247 | * @param array $array  | 
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| 248 | * @return array  | 
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| 249 | */  | 
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| 250 | public static function matches($keys = [], $array = []): array  | 
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| 266 | |||
| 267 | /**  | 
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| 268 | * @param array $array  | 
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| 269 | * @param $findKey  | 
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| 270 | * @param $newKey  | 
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| 271 | * @param $newValue  | 
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| 272 | * @return array|bool  | 
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| 273 | */  | 
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| 274 | public static function insertBefore(array $array, $findKey, $newKey, $newValue)  | 
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| 288 | |||
| 289 | /**  | 
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| 290 | * @param array $array  | 
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| 291 | * @param $findKey  | 
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| 292 | * @param $newKey  | 
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| 293 | * @param $newValue  | 
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| 294 | * @return array|bool  | 
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| 295 | */  | 
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| 296 | public static function insertAfter(array $array, $findKey, $newKey, $newValue)  | 
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| 310 | }  | 
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| 311 | 
This check looks from parameters that have been defined for a function or method, but which are not used in the method body.