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Imploding an array into string

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implode() combines all the array values but looses all the key info: 

$arr = ['a' => "AA", 'b' => "BB", 'c' => "CC"];

echo implode(" ", $arr); // AA BB CC

Imploding keys can be done using array_keys() call: 

$arr = ['a' => "AA", 'b' => "BB", 'c' => "CC"];

echo implode(" ", array_keys($arr)); // a b c

Imploding keys with values is more complex but can be done using functional style: 

$arr = ['a' => "AA", 'b' => "BB", 'c' => "CC"];

echo implode(" ", array_map(function($key, $val) { 
    return "$key:$val"; // function that glues key to the value
}, array_keys($arr), $arr)); 

// Output: a:AA b:BB c:CC
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Arrays:
* Arrays
* Initializing an Array
* Applying a function to each element of an array
* Check if key exists
* Validating the array type
* Iterating multiple arrays together
* Filtering an array
* Removing elements from an array
* Creating an array of variables
* Checking if a value exists in array
* Sorting an Array
* Splitting a string by separators
* Array intersection
* Adding element to start of array
* Merge or concatenate arrays
* ArrayAccess and Iterator Interfaces
* Whitelist only some array keys
* Imploding an array into string
* Split array into chunks
* Exchange values with keys
* Combining two arrays keys from one values from another
* array reduce
* Destructuring arrays using list
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