editing input type file php laravel

i have a form "Add User" where user can add his picture and it works perfectly , but in edit info form where all the records are fetched and shown on the form including the pictures and now suppose if user clicks on update button then input type for file(picture) fields sends an null value

here is the html code

<input type="file" style="position: absolute; top: 0; left: 0; width: 100%; height: 100%; opacity: 0;" name="upload_image" id="upload_image"<?php if(isset($course->imageName)) 
                                                                    echo 'value='.$course['imageName'];
                                    ?> >

even after setting the value to input type field it sends null value to php server

ANY KIND OF HELP IS APPRECIATED

via Chebli Mohamed