Retrieve config values using custom helper

Question

I've stored a set of theme related configuration in a config file.

config/theme.php

// ...

$component = [
  'componentA' = [
    'size' => 'componentDefaultSize',
    'color' => [
      'default' => 'componentDefaultColor',
      'success' => 'componentSuccessColor',
    ]
    'background' => [
      'light' => 'componentLightBackground',
      'dark' => 'componentDarkBackground',
    ]
  ]
];

return [
  // ...
  'component' => $component,
];

This helper function below retrieve related values should the parameters match with keys from theme.php. The parameters are as below

string $type // Type of theme.
string $component // Name of component.
array $properties // Optional properties key name. If not defined, retrieve first array value.

function getTheme(string $type, string $component, array $properties = null)
{
  $theme = null;
  $styles = config("theme.$type.$component");

  foreach ($styles as $style) {
    if (is_array($style)) {

      // If $properties exist retrieve match key value, else retrieve first value of array
      if (isset($properties)) {
        foreach ($style as $key => $class ) {
          foreach ($properties as $property) {
            if ($key == $property) {
              $theme .= $class.' ';
            }
          }
        }
      } else {
        $theme .= $style[0].' '; 
      }
    } else {
      $theme .= $style.' ';
    }
  }
  return $theme;
}

I'm trying to reduce the deep nesting for helper function above but I'm not sure how to achieve that.

Example usage of the helper:

// Without properties
$theme = getTheme('component', 'componentA'); // Return all values and first value of an array

// With properties
$color = 'success';
$theme = getTheme('component', 'componentA', [$color]);

// With multiple properties
$color = 'success';
$background = 'dark';
$theme = getTheme('component', 'componentA', [$color, $background]);

Assistance is much appreciated.

Edited:

1st Attempt:

Toby's comment gave me an idea.

function getTheme(string $type, string $component, array $keys = null)
{
  $theme = null;
  $properties = config("theme.$type.$component");
  foreach ($properties as $property) {
    if (is_array($property) && isset($keys)) {
      if(array_intersect(array_keys($property), $keys)){
        foreach($keys as $key){
          $theme .= $property[$key].' ';
        }
      } else {
        $theme .= reset($property).' ';
      }
    } else if (is_array($property)) {
      $theme .= reset($property).' ';
    } else {
      $theme .= $property.' ';
    }
  }
  return $theme;
}

I switched $properties to $keys for better readability. I still don't like $theme .= reset($property).' '; is called twice.

2nd attempt:

I've managed to refactor it to as below:

function getTheme(string $type, string $component, array $keys = null)
{
  $theme = null;
  $properties = config("theme.$type.$component");
  foreach ($properties as $property) {
    if (is_array($property) && isset($keys)) {
      $theme .= implode(' ', array_values(array_intersect_key($property, array_fill_keys($keys, '')))).' ';
    } else if (is_array($property)) {
      $theme .= reset($property).' ';
    } else {
      $theme .= $property.' ';
    }
  }

  return $theme;
}

Works fine for now but $theme .= implode(' ', array_values(array_intersect_key($property, array_fill_keys($keys, '')))).' '; is a bit of a stretch.

Answer 1

I'll review your 2nd and most recent refactor.

1. Your function getTheme() builds a space-delimited string of class values. Your current function name is clear about the intent, but perhaps a little unclear on the data that it returns. You might consider a more descriptive name or declaring the return type. On the topic of the return type, your function is returning a nullable string. Is there a benefit to returning null? Would you be just as happy to return an empty string? I prefer to reduce the total number of returnable data types so that dependent scripts don't need to juggle as much.

2. I don't ever use nullable array types. An empty array is falsey and I rely on that fact to make functionless conditional checks which makes nullability unnecessary.

3. Because you are using concatenation and appending a space after every class name, you will have a result string with a dangling space. This means your string will either not be perfectly clean, or a trim() call will be necessary. I would, instead, use a temporary array, then implode before returning the value.

4. When writing your looped condition block, handle the easier, negative outcomes first. Processing the non-array $property in the first branch means that you won't need to check the data type again in subsequent branches.

5. As mentioned earlier, you can use !$keys to determine if an array is empty.

6. To mutate the $keys values to keys, you can just flip the array instead of assigning values which will never be used. Do this only once before looping the properties.

7. Use a variadic push array_merge() to merge your filtered associative array of classnames into the temporary array.

8. Oh, and elseif is one word in PHP.

Code:

function getTheme(
    string $type,
    string $component,
    array $keys = []
): string
{
    $classNames = [];
    $properties = config("theme.$type.$component");
    $whitelist = array_flip($keys);
    foreach ($properties as $property)) {
        if (!is_array($property) {
            $classNames[] = $property;
        } elseif (!$keys) {
            $classNames[] = reset($property);
        } else {
            $classNames = array_merge(
                $classNames,
                array_intersect_key($property, $whitelist)
            );
        }
    } 
    return implode(' ', $classNames);    
}