Simplify exists() method with tests and docs

README.md

@@ -405,17 +405,14 @@ $a->each(); // [0 => 0, 'key' => 0, 1 => 'a', 'value' => 'a']
 
 ### exists
 
-A custom contains function where you can supply your own contains function as a closure. 
-The closure must take two parameters, a needle and an element it will be comparing.
+A custom contains method where you can supply your own custom logic in any callable function. 
 
 ``` php
 $a = A::create(['a', 'b', 'c']);
 
-$closure = function($needle, $element) {
-    return $needle === $element;
-};
-
-$a->exists($closure, 'a'); // true
+$a->exists(function($key, $value) {
+   return 1 === $key and 'b' === $value;
+}); // true
 ```
 
 ### export

src/AbstractArray.php

@@ -431,15 +431,14 @@ public function containsKey($key)
     /**
      * Find the given value in the array using a closure
      *
-     * @param callable $callable
-     * @param mixed $needle
+     * @param callable $func
      *
      * @return bool Returns true if the given value is found, false otherwise
      */
-    public function exists(callable $callable, $needle)
+    public function exists(callable $func)
     {
-        foreach ($this->elements as $el) {
-            if ($callable($needle, $el)) {
+        foreach ($this->elements as $key => $value) {
+            if ($func($key, $value)) {
                 return true;
             }
         }

tests/AbstractArrayTest.php

@@ -203,16 +203,14 @@ public function testEach(array $array)
      */
     public function testExists(array $array)
     {
-        $key = 2;
-
-        $closure = function($needle, $element){
-            return $needle === $element;
+        $callable = function($key, $value) {
+            return 2 === $key and 'two' === $value;
         };
 
         $arrayzy = $this->createArrayzy($array);
-        $isContains = in_array($key, $array);
+        $isExists = isset($array[2]) && 'two' === $array[2];
 
-        $this->assertSame($isContains, $arrayzy->exists($closure, $key));
+        $this->assertSame($isExists, $arrayzy->exists($callable));
     }
 
     /**