HTTP Headers

http_headers.php

<?php

class Headers implements ArrayAccess {
    private static $headers = array(
        'Accept',
        'Accept-Charset',
        'Accept-Language',
        'Accept-Encoding',
        'Authorization',
        'Cache-Control',
        'Connection',
        'Cookie',
        'Content-Length',
        'Content-Type',
        'Content-MD5',
        'User-Agent',
        'Referer',
        'Expect',
        'Host',
        'If-Match',
        'If-None-Match',
        'If-Modified-Since',
        'If-Unmodified-Since',
        'If-Range',
        'X-Requested-With',
        'X-Forwarded-Proto',
        'X-Forwarded-For',
        'X-HTTP-Method-Override',
    );

    private $server;

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

    public function offsetExists($offset) {
        return isset($this->server[$this->normalize($offset)]);
    }

    public function offsetGet($offset) {
        return $this->server[$this->normalize($offset)];
    }

    public function offsetSet($offset, $value) {
        $this->server[$this->normalize($offset)] = $value;
    }

    public function offsetUnset($offset) {
        unset($this->server[$this->normalize($offset)]);
    }

    private function normalize($offset) {
        if (!in_array($offset, static::$headers, true)) {
            throw new InvalidArgumentException(
                "Invalid header, $offset given"
            );
        }

        if (strpos($offset, 'Content-') === 0) {
            return 'CONTENT_' . strtoupper(substr($offset, 8));
        }

        return 'HTTP_' . strtoupper(strtr($offset, '-', '_'));
    }
}

http_headers_test.php

<?php

class HeadersTest extends \PHPUnit_Framework_TestCase {
    private $server = array(
        'REQUEST_URI'          => '/',
        'REQUEST_METHOD'       => 'GET',
        'HTTP_HOST'            => 'localhost',
        'HTTP_USER_AGENT'      => 'Mozilla/5.0',
        'HTTP_ACCEPT'          => 'text/html;q=0.9,*/*;q=0.8',
        'HTTP_ACCEPT_LANGUAGE' => 'en-US,en;q=0.5',
        'HTTP_ACCEPT_ENCODING' => 'gzip, deflate',
        'HTTP_CONNECTION'      => 'keep-alive',
        'HTTP_CACHE_CONTROL'   => 'max-age=0',
    );

    public function getInvalidHeader() {
        return array(
            [new stdClass],
            [function() {}],
        );
    }

    public function getInexistentHeader() {
        return array(
            ['Content-Ravioli'],
        );
    }

    public function testConstructorWithArray() {
        new Headers($this->server);
    }

    public function testConstructorWithArrayAccess() {
        new Headers(new ArrayObject($this->server));
    }

    public function testExists() {
        $headers = new Headers($this->server);

        $this->assertTrue(isset($headers['Host']));
        $this->assertFalse(isset($headers['Referer']));
    }

    public function testGet() {
        $headers = new Headers($this->server);

        $this->assertEquals('text/html;q=0.9,*/*;q=0.8', $headers['Accept']);
        $this->assertEquals('en-US,en;q=0.5', $headers['Accept-Language']);
    }

    /**
     * @dataProvider      getInvalidHeader
     * @expectedException PHPUnit_Framework_Error
     */
    public function testGetWithInvalidOffset($invalid) {
        $headers = new Headers($this->server);
        $headers[$invalid];
    }

    /**
     * @dataProvider      getInexistentHeader
     * @expectedException InvalidArgumentException
     */
    public function testGetWithInexistentOffset($inexistent) {
        $headers = new Headers($this->server);
        $headers[$inexistent];
    }

    public function testSet() {
        $headers = new Headers($this->server);
        $headers['Content-Type'] = 'text/html';

        $this->assertEquals('text/html', $headers['Content-Type']);
    }

    public function testUnset() {
        $headers = new Headers($this->server);
        $headers['Content-Type'] = 'text/html';

        unset($headers['Accept-Language']);
        unset($headers['Content-Type']);

        $this->assertFalse(isset($headers['Accept-Language']));
        $this->assertFalse(isset($headers['Content-Type']));
    }
}