cross join arrays to generate data for test scenarios

Question

I'm trying to cross join arrays to automatically create data for various test scenarios in an app. Here are the arrays to be cross joined (note that $base['sales'] has had some elements stripped out of it to simplify it for posting this question):

$base['sales'] = ['shirts'=>1200.0, 'pants'=>1000.0, 'socks'=>1700.0];

$scenarioIDs = range(1, 5);

The end result is supposed to look like this:

$data[1]['sales'] = ['shirts'=>1200.0, 'pants'=>1000.0, 'socks'=>1700.0];
$data[2]['sales'] = ['shirts'=>1200.0, 'pants'=>1000.0, 'socks'=>1700.0];
$data[3]['sales'] = ['shirts'=>1200.0, 'pants'=>1000.0, 'socks'=>1700.0];
$data[4]['sales'] = ['shirts'=>1200.0, 'pants'=>1000.0, 'socks'=>1700.0];
$data[5]['sales'] = ['shirts'=>1200.0, 'pants'=>1000.0, 'socks'=>1700.0];

I have tried this:

    $data = [];
    array_map(function($scenarioID) {
        $data[$scenarioID]['sales'] = $base['sales'];
    }, $scenarioIDs);
echo '<pre>' . print_r($data, 1) . '</pre>';    
exit();

but get the message Undefined variable: base in C:\xampp\htdocs\Sales\index.php on line 72 five times (one for each scenarioID).

I keep thinking there must be a way to do this without using loops. Does anyone know how?

Possible duplicate of [php variables in anonymous functions](https://stackoverflow.com/questions/11420520/php-variables-in-anonymous-functions) — Ruslan Osmanov, Aug 09 '17 at 02:57

BeetleJuice · Accepted Answer · 2017-08-09T03:11:47.243

To use a variable from the exterior context within your anonymous function, you need the use keyword:

array_map(
  function($id) use ($base, &$data) {/* fill out the function */},
  $scenarioIDs
);

This syntax will make a copy of $base at the time the function is first invoked, so if you make changes to $base and try to use the same custom mapper, the new values of $base will not be reflected. So, if you need the anonymous function to always work with the current value of $base, then pass that argument by reference as I did with $data:

function($id) use (&$base, &$data) {}

From the docs:

Closures may also inherit variables from the parent scope. Any such variables must be passed to the use language construct.

As a sidenote, array_map is meant to transform the supplied array ($scenarioIDs in your case) into a different array. You aren't really using it as it was meant. If all you want to do is attach the scenario ids as keys to $data, just use this one-liner:

foreach($scenarioIDs as $id) $data[$id]['sales'] = $base['sales'];

cross join arrays to generate data for test scenarios

1 Answers1