Error Handling for Dynamic Twitter Signature Images with PHP

Before we begin, let’s take a moment to examine the fully operational class.

class SignatureImage

{

    private $screen_name;

    private $profile_image;

    private $status_text;

    private $local_avatar;

    public function __construct($name, $bg_image, $adir)

    {

        $this->fetchUserInfo(strtolower($name));

        $this->fetchAvatar($this->profile_image, $adir);

        $this->renderImage();

    }

    private function fetchUserInfo($name)

    {

        $url = "http://twitter.com/statuses/user_timeline/{$name}.xml?count=1";

        $xml = $this->curlRequest($url);

        if ($xml === false) {

            // User feed unavailable.

        }

        $statuses = new SimpleXMLElement($xml);

        if (!$statuses || !$statuses->status) {

            // Invalid user channel.

        }

       foreach ($statuses->status as $status) {

            $this->status_text   = (string) $status->text;

            $this->profile_image = (string) $status->user->profile_image_url;

            $this->screen_name   = (string) $status->user->screen_name;

            break;

        }

    }

    private function curlRequest($url)

    {

        if (!extension_loaded('curl')) {

            // PHP extension CURL is not loaded.

        }

        $curl = curl_init($url);

        curl_setopt($curl, CURLOPT_HEADER, false);

        curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

        $result = curl_exec($curl);

        if (curl_errno($curl) !== 0 || curl_getinfo($curl, CURLINFO_HTTP_CODE) !== 200) {

            $result === false;

        }

        curl_close($curl);

        return $result;

    }

    private function fetchAvatar($url, $adir)

    {

        $parts      = explode('/', $url);

        $fname      = end($parts);

        $adir       = preg_match('#^(.*?)/$#i', $url) ? $adir : "{$adir}/";

        $fname      = $adir . $fname;

        if (!file_exists($fname)) {

            $img = $this->curlRequest($url);

            $fp = fopen($fname, 'w');

            fwrite($fp, $img);

            fclose($fp);

        }

        $this->local_avatar = $fname;

    }

}

    private function renderImage($bg_image)

    {

        if (!function_exists('gd_info')) {

            // No GD support.

        }

        $margin_left = 11;

        $margin_bottom = 6;

        $image = @imagecreatefromjpeg($bg_image);

        if (!$image) {

            // Unable to create image.

        }

        $this->embedAvatar($image, $this->local_avatar, $margin_left, $margin_bottom);

        $string = "{$this->screen_name}: {$this->status_text}";

        $this->embedText($image, $string, $margin_left, $margin_bottom);

        header("Content-type: image/jpeg");

        $created = @imagejpeg($image);

        if (!$created) {

            // Unable to finalize image.

        }

        @imagedestroy($image);

    }

    private function embedAvatar(&$image, $avatar, $left, $bottom)

    {

        if (file_exists($avatar)) {

            if (stristr($avatar, '.jpg')) {

                $aimg = @imagecreatefromjpeg($avatar);

            } elseif (stristr($avatar, '.png')) {

                $aimg = @imagecreatefrompng($avatar);

            }

            if (!$aimg) {

                // Unable to create avatar.

            }

            $awidth  = imagesx($aimg);

            $aheight = imagesy($aimg);

            $top     = imagesy($image) - $aheight - $bottom;

            $copied  = @imagecopy($image, $aimg, $left, $top, 0, 0, $awidth, $aheight);

            if (!$copied) {

            // Unable to add avatar to image.

            }

        }

    }

    private function embedText(&$image, $text, $left, $top, $tmaxw=300, $font=3)

    {

        $fheight = imagefontheight($font);

        $color   = imagecolorallocate($image, 100, 100, 100);

        $lines   = $this->lineWrap($font, $text, $tmaxw);

        $lmax    = floor(imagesy($image) / $fheight);

        $lcount  = (count($lines) > $lmax) ? $lmax : count($lines);

        $ttop    = (imagesy($image) - ($lcount*$fheight)) / 2;

        $tleft   = 2*$left + 48;

        while ((list($num, $line) = each($lines)) && $num < $lcount) {

            imagestring($image, $font, $tleft, $ttop, $line, $color);

            $ttop += $fheight;

        }

    }

    private function lineWrap($font, $text, $maxwidth)

    {

        $fwidth  = imagefontwidth($font);

        if ($maxwidth != NULL) {

            $maxcharsperline = floor($maxwidth / $fwidth);

            $text = wordwrap($text, $maxcharsperline, "n", 1);

        }

        return explode("n", $text);

    }

}

isset($_GET['name']) or die('You must provide a user name.');

new SignatureImage($_GET['name'], 'banners/my_banner.jpg', 'avatars', 'cache');

This class already employs pretty thorough error-catching.  Throughout the code I’ve used comments to indicate error states.  Today we’ll be replacing those comments with actual error-handling code in order to make this a fully functional OOP class.