Yes. It is possible to display the file names (not the files) in a table using readdir.
No. Readdir is returning one file name, so it is not possible to get readdir to display more than one file name. And it is not possible to get readdir to format the output. You have to do that yourself.
Basically there are two ways to solve this. One is to build a table and place the file names in it using readdir. The other way is to make an array with file names, then build a table using the array. With as many posts as you have it should be possible for you to create this yourself.