File Handling using <option value=""></option>

["AdonaiEchad"]

I am having a hard time trying to figure out how to work a file handling.
 I am able to upload a file to a specific directory (e.g. _assets/professors/)

 I have an insert php page where I enter a professor's name in a form field and 
I want to use the <option value="">List Content In Folder Directory</option> to 
choose the image in the folder directory that has been uploaded in Ascending 
order. 
 <select name="photo" id="photo"> *
 <option value="N/A">N/A</option>
 </select>