PHP Amazon S3 access private files through URL

I'm using AWS PHP sdk to save images on S3. Files are saved privately. Then, I'm showing the image thumbnails using the S3 file url in my web application but since the files are private so the images are displayed as corrupt.

When the user clicks on the name of file, a modal is opened to show the file in larger size but file is displayed as corrupt there as well due to the same issue.

Now, I know that there are two ways to make this working. 1. Make the files public. 2. Generate pre-signed urls for files. But I cannot go with any of these two options due to the requirements of my project.

My question is that is there any third way to resolve this issue?