Validating file types

…In this movie, we'll learn how to use PHP…to allow only certain file types to be uploaded.…When we're validating file types, what we're talking…about is restricting uploads to specific file types.…The idea is to whitelist the file types that…we want to allow, and thereby disallow everything else.…So if we're expecting to get an image file,…then we would whitelist, only, the image file types.…If we want only PDFs, we would whitelist, only, PDFs.…This then, becomes a question of how do you tell a good file from a bad file?…It's not as easy it it first sounds.…

What if you have a text file?…Do you change the extension in the file name to .jpg?…It now looks like an image file if you just look at the file name.…Or what if you have a file that has two endings?…What if it's .php.jpg?…Or worse, what if you have a file that's a legitimate…image file which also contains hidden PHP code inside of it?…I'm sad to say that that is possible.…There is no bulletproof solution to validating file types.…So instead, we're going to deploy a number of different measures to try…