php - Merging by array value (and doing calculations with the other keys) -

i'm having difficult time finding viable solution problem:

this array have, , want group array product_name , count quantity. array structure needs remain same.

array( [0] => array     (         [product_quantity] => 1         [product_name] => appel     )  [1] => array     (         [product_quantity] => 1         [product_name] => d-day     )  [2] => array     (         [product_quantity] => 4         [product_name] => d-day     )  [3] => array     (         [product_quantity] => 2         [product_name] => d-day     )  [4] => array     (         [product_quantity] => 1         [product_name] => emiel     )  [5] => array     (         [product_quantity] => 9         [product_name] => emiel     )  [6] => array     (         [product_quantity] => 3         [product_name] => estella     )  [7] => array     (         [product_quantity] => 4         [product_name] => feeke     )  [8] => array     (         [product_quantity] => 1         [product_name] => feeke     )  [9] => array     (         [product_quantity] => 7         [product_name] => reset     )  [10] => array     (         [product_quantity] => 1         [product_name] => reset     )) 

what need output:

array(     [0] => array         (             [product_quantity] => 1             [product_name] => appel         )      [1] => array         (             [product_quantity] => 7             [product_name] => d-day         )      [2] => array         (             [product_quantity] => 10             [product_name] => emiel         )      [3] => array         (             [product_quantity] => 3             [product_name] => estella         )      [4] => array         (             [product_quantity] => 5             [product_name] => feeke         )      [5] => array         (             [product_quantity] => 8             [product_name] => reset         )     ) 

i love hear advice, or solutions on how tackle this!

the goal can reached in many ways. if aim speed use foreach iterate on input array, incrementally computing , storing values new array (the body of callback function below).

if aim impress workmates or recruiter knowledge of php use array_reduce():

$output = array_values(         // don't need keys of generated array     array_reduce(               // incrementally process $input using callback         $input,         // $carry partial result         // $item processed item         function(array $carry, array $item) {             // extract product name local variable             // we'll use several times below             $name = $item['product_name'];             // if it's new product initialize entry in output             if (! array_key_exists($name, $carry)) {                 $carry[$name] = array(                     'product_quantity' => 0,                     'product_name'     => $name,                 );             }             // update quantity of group             $carry[$name]['product_quantity'] += $item['product_quantity'];             // return partial result             return $carry;         },         // start empty array         array()     ) ); 

update

the op asked in comment how reuse callback function , make customizable ("how use parameter make 'product_name' dynamicaly?").

you can put value ('product_name') variable ($key) outside function , use use language construct let anonymous function inherit it.

$key = 'product_name';            // values needs in variable $output = array_values(     array_reduce(         $input,         // 'use' keyword lets anonymous function use copy of $key         function(array $carry, array $item) use ($key) {             $name = $item[$key];             // rest of callback's code comes here unchanged             // ...             // return partial result             return $carry;         },         array()     ) ); 

see example #3 on documentation of anonymous functions more examples.

you can store callback function variable. doesn't improve readability of code. however, keep reading, intermediate step, real magic happens below.

$key = 'abc'; $f = function(array $carry, array $item) use ($key) {     $name = $item[$key];     // rest of callback's code comes here unchanged     // ...     // return partial result     return $carry; };  $output = array_values(array_reduce($input, $f, array())); 

to make reusable need have way generate callbacks different values of $key. let's write simple function creates parametrized callbacks:

// function creates new callback uses value of argument $key function makefn($key) {     return function(array $carry, array $item) use ($key) {         $name = $item[$key];         // rest of callback's code comes here unchanged         // ...         // return partial result         return $carry;     }; } 

now, let's use new function. creates different callback functions can used reduce array using various keys:

$output1 = array_values(array_reduce($input, makefn('product_name'), array())); $output2 = array_values(array_reduce($input, makefn('product_code'), array()));