mailgun-php/Mailgun/Guzzle/Http/Message/PostFile.php

<?php

namespace Guzzle\Http\Message;

use Guzzle\Common\Version;
use Guzzle\Common\Exception\InvalidArgumentException;
use Guzzle\Http\Mimetypes;

/**
 * POST file upload
 */
class PostFile implements PostFileInterface
{
    protected $fieldName;
    protected $contentType;
    protected $filename;

    /**
     * @param string $fieldName   Name of the field
     * @param string $filename    Path to the file
     * @param string $contentType Content-Type of the upload
     */
    public function __construct($fieldName, $filename, $contentType = null)
    {
        $this->fieldName = $fieldName;
        $this->setFilename($filename);
        $this->contentType = $contentType ?: $this->guessContentType();
    }

    public function setFieldName($name)
    {
        $this->fieldName = $name;

        return $this;
    }

    public function getFieldName()
    {
        return $this->fieldName;
    }

    public function setFilename($filename)
    {
        // Remove leading @ symbol
        if (strpos($filename, '@') === 0) {
            $filename = substr($filename, 1);
        }

        if (!is_readable($filename)) {
            throw new InvalidArgumentException("Unable to open {$filename} for reading");
        }

        $this->filename = $filename;

        return $this;
    }

    public function getFilename()
    {
        return $this->filename;
    }

    public function setContentType($type)
    {
        $this->contentType = $type;

        return $this;
    }

    public function getContentType()
    {
        return $this->contentType;
    }

    public function getCurlValue()
    {
        // PHP 5.5 introduced a CurlFile object that deprecates the old @filename syntax
        // See: https://wiki.php.net/rfc/curl-file-upload
        if (function_exists('curl_file_create')) {
            return curl_file_create($this->filename, $this->contentType, basename($this->filename));
        }

        // Use the old style if using an older version of PHP
        $value = "@{$this->filename};filename=" . basename($this->filename);
        if ($this->contentType) {
            $value .= ';type=' . $this->contentType;
        }

        return $value;
    }

    /**
     * @deprecated
     * @codeCoverageIgnore
     */
    public function getCurlString()
    {
        Version::warn(__METHOD__ . ' is deprecated. Use getCurlValue()');
        return $this->getCurlValue();
    }

    /**
     * Determine the Content-Type of the file
     */
    protected function guessContentType()
    {
        return Mimetypes::getInstance()->fromFilename($this->filename) ?: 'application/octet-stream';
    }
}