I'm making a page where the user upload a file. I want an if statement to create an $error variable if the file type is anything other jpg, gif, and pdf.

Here's my code:

$file_type = $_FILES['foreign_character_upload']['type']; //returns the mimetype

if(/*$file_type is anything other than jpg, gif, or pdf*/) {
  $error_message = 'Only jpg, gif, and pdf files are allowed.';
  $error = 'yes';
}

I'm having difficulty structuring the if statement. How would I say that?