<form method="POST">
    <h3>Editing: IdentificationHeader.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Mime\Header;

use Symfony\Component\Mime\Address;
use Symfony\Component\Mime\Exception\RfcComplianceException;

/**
 * An ID MIME Header for something like Message-ID or Content-ID (one or more addresses).
 *
 * @author Chris Corbyn
 */
final class IdentificationHeader extends AbstractHeader
{
    private $ids = [];
    private $idsAsAddresses = [];

    /**
     * @param string|array $ids
     */
    public function __construct(string $name, $ids)
    {
        parent::__construct($name);

        $this-&gt;setId($ids);
    }

    /**
     * @param string|array $body a string ID or an array of IDs
     *
     * @throws RfcComplianceException
     */
    public function setBody($body)
    {
        $this-&gt;setId($body);
    }

    public function getBody(): array
    {
        return $this-&gt;getIds();
    }

    /**
     * Set the ID used in the value of this header.
     *
     * @param string|array $id
     *
     * @throws RfcComplianceException
     */
    public function setId($id)
    {
        $this-&gt;setIds(\is_array($id) ? $id : [$id]);
    }

    /**
     * Get the ID used in the value of this Header.
     *
     * If multiple IDs are set only the first is returned.
     */
    public function getId(): ?string
    {
        return $this-&gt;ids[0] ?? null;
    }

    /**
     * Set a collection of IDs to use in the value of this Header.
     *
     * @param string[] $ids
     *
     * @throws RfcComplianceException
     */
    public function setIds(array $ids)
    {
        $this-&gt;ids = [];
        $this-&gt;idsAsAddresses = [];
        foreach ($ids as $id) {
            $this-&gt;idsAsAddresses[] = new Address($id);
            $this-&gt;ids[] = $id;
        }
    }

    /**
     * Get the list of IDs used in this Header.
     *
     * @return string[]
     */
    public function getIds(): array
    {
        return $this-&gt;ids;
    }

    public function getBodyAsString(): string
    {
        $addrs = [];
        foreach ($this-&gt;idsAsAddresses as $address) {
            $addrs[] = '&lt;'.$address-&gt;toString().'&gt;';
        }

        return implode(' ', $addrs);
    }
}
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