strategySolution.php

<?php

class Context
{
    private $strategy;

    public function __construct(StrategyInterface $strategy)
    {

        $this->strategy = $strategy;
    }

    public function applyStrategy(Book $book)
    {
        return $this->strategy->formatTitle($book);
    }
}

interface StrategyInterface
{
    public function formatTitle(Book $book);
}

class StrategyUppercase implements StrategyInterface
{
    public function formatTitle(Book $book)
    {
        return strtoupper($book->getTitle());
    }
}

class StrategyLowercase implements StrategyInterface
{
    public function formatTitle(Book $book)
    {
        return strtolower($book->getTitle());
    }
}

class StrategyLcfirst implements StrategyInterface
{
    public function formatTitle(Book $book)
    {
        return lcfirst($book->getTitle());
    }
}

class StrategyUcwords implements StrategyInterface
{
    public function formatTitle(Book $book)
    {
        return ucwords($book->getTitle());

    }
}

class Book
{
    private $title;

    function __construct(string $title_in)
    {
        $this->title = $title_in;
    }

    function getTitle(): string
    {
        return $this->title;
    }
}

$book = new Book('Harry Potter');
echo "Title: " . $book->getTitle()."<br/>";

$strategyUppercase = new StrategyUppercase();
$context = new Context($strategyUppercase);
echo "Strategy uppercase: " . $context->applyStrategy($book)."<br/>";

$strategyLowercase = new StrategyLowercase();
$context = new Context($strategyLowercase);
echo "Strategy lowercase: " . $context->applyStrategy($book)."<br/>";

$strategyLcfirst = new StrategyLcfirst();
$context = new Context($strategyLcfirst);
echo "Strategy first character in lowercase: " . $context->applyStrategy($book)."<br/>";


/**** Output: ***************************************
* Title: Harry Potter
* Strategy uppercase: HARRY POTTER
* Strategy lowercase: harry potter
* Strategy first character in lowercase: harry Potter
*****************************************************/