PHP + Imagick =脚本头过早结束？

RewriteEngine on
RewriteBase /
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^(.*)\\.jpg /images/image.php?%{REQUEST_FILENAME}

<?php
/*
 * Watermark module
 * Uses ImageMagick lib
 * 
 */

// The name of the watermark image. Should be in the same directory
// as the image.php
define(\'WATERMARK_IMAGE\', \'watermark.png\');

// Watermark images with larger width than this value (pixel)
// Set to 0 (Zero) to watermark all images
define(\'WATERMARK_THRESHOLD_WIDTH\', 218);

$filename = $_SERVER[\'QUERY_STRING\'];


// If the requested file doesn\'t exist, return HTTP 404
// Should not happen, as the htaccess handles that
if (file_exists($filename))
{
    // Get the last modified property of the source file for caching
    $file_last_modified = filemtime($filename);
    // Expirese in two months
    $expires = time() + (60 * 24 * 60 * 60);

    // Checking last modified date, if it\'s the same, then return 304 \"Not Modified\"
    // No body response is generated.
    if (isset($_SERVER[\'HTTP_IF_MODIFIED_SINCE\']) 
        && strtotime($_SERVER[\'HTTP_IF_MODIFIED_SINCE\']) >= $file_last_modified)
    {
        header(\"HTTP/1.1 304 Not Modified\");
    }
    else
    {
        $requested_image = new Imagick($filename);

        // If the marker image doesn\'t exist, then return the original image
        if (file_exists(WATERMARK_IMAGE))
        {

            $watermark = new Imagick(WATERMARK_IMAGE);

            // Get original image\'s dimensions
            $requested_image_width = $requested_image->getImageWidth();
            $requested_image_height = $requested_image->getImageHeight();

            // Get watermark image\'s dimensions
            $watermark_width = $watermark->getImageWidth();
            $watermark_height = $watermark->getImageHeight();

            // Calculate watermark position
            // Current position: center - center
            $position_x = ($requested_image_width - $watermark_width)/2;
            $position_y = ($requested_image_height - $watermark_height)/2;

            // Only watermark images larger than the threshold
            if ($requested_image_width > WATERMARK_THRESHOLD_WIDTH)
            {
                $requested_image->compositeImage($watermark, imagick::COMPOSITE_OVERLAY, $position_x, $position_y);
            }

            // Destroy the marker image
            $watermark->destroy();
        }

        // Set the headers
        header(\"Pragma: public\");
        header(\"Content-type: image/jpeg\");
        header(\"Expires: \" . gmdate(\"D, d M Y H:i:s\", $expires) . \" GMT\");
        header(\"Last-Modified: \" . gmdate(\"D, d M Y H:i:s\", $file_last_modified) . \" GMT\");

        // Return the response image
        echo $requested_image;

        // Destroy the temporary image
        $requested_image->destroy();
    }
}
else
{
    header(\'HTTP/1.1 404 Not Found\');
}

/* End of file image.php */
/* Location: ./images/image.php */