Flowplayer视频源错误

I have a PHP script that helps me display a video with Flowplayer.

$filepath =  str_replace('/','\\', $_SERVER['DOCUMENT_ROOT']. VIDEO_PATH . $video->video_path_original_quality);

gives me filepath as

C:\wamp\www\XYZ\admin\uploads\videos\video-800-old_original.mp4

where VIDEO_PATH = XYZ\admin\uploads\videos.

My problem is that the video source in my HTML still shows a blank value. The code I have written is

<video>
          <source type="video/mp4" src="<?php str_replace('/','\\',$filepath);?>"/>

Can anybody let me know what's wrong ? I have tried 'echo' as well, but it doesn't help either. I am working on Codeigniter

You don't echo anything:

<?php str_replace…

should be:

<?php echo str_replace…

or, more typically:

<?= str_replace…