Real-life example of Closure usage with PHP5.3

One of the new improvements in new PHP5.3 version are the Closures. Here you are a real-life example where closures are really useful for me. Imagine the following scenario. A very common scenario at least in my daily work. We have a recordset from a SQL:

$recordset = array(
    array('code' => 1, 'quantity' => 20, 'amount' => 2),
    array('code' => 2, 'quantity' => 30, 'amount' => 3),
    array('code' => 3, 'quantity' => 10, 'amount' => 1),
    array('code' => 4, 'quantity' => 20, 'amount' => 5),
);

Imagine we want to show the recordset into a datagrid but we also want to calculate the price (quality / amount) of each row and add a total. We can perform the operation within the SQL but I prefer to keep the SQLs as simple as I can and let the logic to PHP.

We can use array_walk to calculate the price but with PHP<5.3 we needed to pass the callback function as a string. A dirty trick. Maybe a simple foerach is a better solution, isn’t it?. Now with PHP5.3 we can create anonymous functions (aka Closures) in the finest JavaScript style. They are really cool. We even can use the ‘use’ statement to use variables outside Closuse’s scope. This attribute allows us in our example to calculate our totals.

Maybe is difficult to explain but the code is very clear:

$total = array('quantity' => 0, 'amount' => 0, 'price' => null);
array_walk($recordset, function (&$value) use(&$total){
    $value['price'] = ($value['amount'] == 0) ? null : $value['quantity'] / $value['amount'];
    $total['quantity'] += $value['quantity'];
    $total['amount'] += $value['amount'];
});
$total['price'] = ($total['amount'] == 0) ? null : $total['quantity'] / $total['amount'];

And now our $recordset array will have an extra item called register and we have created a new row for our recordset with total values.

recordset:

Array(
 [0]=>Array(=>1 [quantity]=>20 [amount]=>2 [price]=>10)
 [1]=>Array(=>2 [quantity]=>30 [amount]=>3 [price]=>10)
 [2]=>Array(=>3 [quantity]=>10 [amount]=>1 [price]=>10)
 [3]=>Array(=>4 [quantity]=>20 [amount]=>5 [price]=>4)
)

total:

Array(
 [quantity] => 80 [amount]=>11 [price] => 7.2727272727273
)