Key-Based Collection Comparison with Laravel's diffKeys Method

Laravel's collection system includes the powerful diffKeys method, helping you identify differences between collections based on their keys rather than values.

Basic Usage

Compare collections by their keys:

$collection = collect([
    'one' => 10,
    'two' => 20,
    'three' => 30,
    'four' => 40,
    'five' => 50,
]);

$diff = $collection->diffKeys([
    'two' => 2,
    'four' => 4,
    'six' => 6,
]);

// Result: ['one' => 10, 'three' => 30, 'five' => 50]

Real-World Example

Here's how you might use it in a configuration manager:

class ConfigurationManager
{
    public function findRemovedSettings(array $oldConfig, array $newConfig)
    {
        return collect($oldConfig)
            ->diffKeys($newConfig)
            ->map(function ($value, $key) {
                return [
                    'key' => $key,
                    'old_value' => $value,
                    'removed_at' => now()
                ];
            });
    }

    public function validateRequiredKeys(array $config)
    {
        $required = [
            'database' => null,
            'cache' => null,
            'queue' => null
        ];

        $missing = collect($required)
            ->diffKeys($config)
            ->keys();

        if ($missing->isNotEmpty()) {
            throw new InvalidConfigurationException(
                'Missing required configuration keys: ' . 
                $missing->implode(', ')
            );
        }

        return true;
    }

    public function syncConfigurations(array $source, array $target)
    {
        $added = collect($source)->diffKeys($target);
        $removed = collect($target)->diffKeys($source);

        return [
            'added' => $added->all(),
            'removed' => $removed->all(),
            'changes' => $added->count() + $removed->count()
        ];
    }
}

The diffKeys method makes it easy to track changes and validate configurations based on their keys.

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