CODESAMPLE

Facade - PHP

Facade PHP

The Facade pattern provides a simplified interface to a complex subsystem. It defines a high-level interface that hides the intricacies of the underlying components. This makes the subsystem easier to use for clients who don’t need to know the details.

The code demonstrates a VideoConversionFacade that encapsulates the complexity of video conversion – including file format checking, codec selection, and actual conversion using separate FileFormatChecker, CodecFactory, and VideoConverter classes. Clients interact only with the Facade, simplifying their code and reducing dependencies on the subsystem’s internal workings. This is idiomatic PHP as it leverages classes to represent components and promotes loose coupling through a dedicated interface, enhancing maintainability and testability.

<?php

/**
 * Subsystem classes - these are complex and clients shouldn't interact with them directly.
 */
class FileFormatChecker {
    public function isValid(string $file): bool {
        // Simulate format checking
        return strtolower(pathinfo($file, PATHINFO_EXTENSION)) === 'mp4';
    }
}

class CodecFactory {
    public function createCodec(string $format): Codec {
        // Simulate codec creation based on format
        if ($format === 'h264') {
            return new H264Codec();
        }
        return new MPEG4Codec();
    }
}

interface Codec {
    public function encode(string $file): string;
}

class H264Codec implements Codec {
    public function encode(string $file): string {
        return "Encoding $file to H.264";
    }
}

class MPEG4Codec implements Codec {
    public function encode(string $file): string {
        return "Encoding $file to MPEG4";
    }
}

class VideoConverter {
    private Codec $codec;

    public function __construct(Codec $codec) {
        $this->codec = $codec;
    }

    public function convert(string $file, string $format): string {
        return $this->codec->encode($file);
    }
}

/**
 * The Facade class.
 */
class VideoConversionFacade {
    private FileFormatChecker $formatChecker;
    private CodecFactory $codecFactory;
    private VideoConverter $converter;

    public function __construct() {
        $this->formatChecker = new FileFormatChecker();
        $this->codecFactory = new CodecFactory();
    }

    public function convertVideo(string $file, string $format): string {
        if (!$this->formatChecker->isValid($file)) {
            return "Invalid file format.";
        }

        $codec = $this->codecFactory->createCodec($format);
        $this->converter = new VideoConverter($codec);

        return $this->converter->convert($file, $format);
    }
}

// Client code
$facade = new VideoConversionFacade();
echo $facade->convertVideo("video.mp4", "h264") . "\n";
echo $facade->convertVideo("image.jpg", "h264") . "\n";

?>